Growth failure and outcome in Rett syndrome: specific growth references

Exploring the Genetic Role of MECP2 Mutations on Phenotypic Presentation in Males: A Case Report

OBJECTIVE

The purpose of this study was to explore the genotypic and phenotypic presentation of males with MECP2-related neurodevelopmental disorders. When variants in the MECP2 gene are discovered in patients, Rett syndrome becomes a possible diagnosis. Rett syndrome, however, does not encapsulate all phenotypic variations in MECP2 gene mutations, and specific diagnosis can become tricky especially in the male population as mutations in the gene were historically thought to affect females only. The authors present a rare case of a male with a previously unpublished genetic variant resulting in a distinct clinical presentation not meeting the criteria for typical or atypical Rett syndrome.

METHODS

This patient's institutional electronic medical record was accessed, and information was reviewed.

RESULTS

It was discovered that this patient had a maternally inherited variant in his MECP2 gene, resulting in a unique and previously undescribed form of MECP2-related neurodevelopmental disorder, presenting with language regression followed by speech apraxia and motor discoordination.

DISCUSSION/CONCLUSION

Literature reports on various phenotypes associated with MECP2 gene mutations and elaborates on previously identified forms of typical and atypical Rett syndrome. Through this case report, the authors uncovered a pathogenic variant in MECP2 resulting in a rare phenotype of MECP2-related neurodevelopmental disorder that has not previously been described. This should encourage clinicians to think more broadly when approaching diagnosis of children with developmental differences. This also reinforces that Rett syndrome or MECP2 mutations can often present on a spectrum, and it may be beneficial to modify diagnostic criteria to reflect this.

Middle-Aged Women With Rett Syndrome: Longitudinal Profile From the British Isles Rett Syndrome Survey and Suggestions for Care

BACKGROUND AND METHODS

We report historical information from longitudinal data held in the British Isles Rett Syndrome Survey (BIRSS) concerning women of at least 40 years. This information, including comments on the quality of care, has been provided by families, carers, and clinicians.

RESULTS

Information was available on 30 women with a clinical diagnosis of Rett syndrome (RTT), of whom 24 were < 50 years. Twenty-nine women were diagnosed with classic RTT and one with atypical RTT. Of 18 women tested for MECP2 mutations, pathogenic variants were identified in 14. There was little increase in severity over time.

CONCLUSIONS

The study found that: (1) milder phenotypes were common; (2) depression may be under-recognised; (3) menopause does not seem to occur early; (4) nutrition standards from the general population will often be inapplicable; (5) multiple opportunities exist to prevent functional decline through detailed attention to the quality of the medical and social care.

The evolution of nutrition management in children with severe neurological impairment with a focus on cerebral palsy

Nutritional management of children with severe neurological impairment (SNI) is highly complex, and the profile of this population is changing. The aim of this narrative review was to give the reader a broad description of evolution of the nutritional management of children with SNI in a high resource setting. In the last decade, there has been an emphasis on using multiple anthropometric measures to monitor nutritional status in children with SNI, and several attempts at standardising the approach have been made. Tools such as the Feeding and Nutrition Screening Tool, the Subjective Global Nutrition Assessment, the Eating and Drinking Ability Classification System and the Focus on Early Eating and Drinking Swallowing (FEEDS) toolkit have become available. There has been an increased understanding of how the gut microbiome influences gastrointestinal symptoms common in children with SNI, and the use of fibre in the management of these has received attention. A new diagnosis, 'gastrointestinal dystonia', has been defined. The increased use and acceptance of blended food tube feeds has been a major development in the nutritional management of children with SNI, with reported benefits in managing gastrointestinal symptoms. New interventions to support eating and drinking skill development in children with SNI show promise. In conclusion, as the life expectancy of people with SNI increases due to advances in medical and nutrition care, our approach necessitates a view to long-term health and quality of life. This involves balancing adequate nutrition to support growth, development and well-being while avoiding overnutrition and its associated detrimental long-term effects.

The Management of Bone Defects in Rett Syndrome

Rett syndrome (RS) is a rare neurodevelopmental disorder primarily caused by mutations in the X-linked methyl-CpG binding protein 2 (MECP2) gene, responsible for encoding MECP2 which plays a pivotal role in regulating gene expression. The neurological and non-neurological manifestations of RS vary widely in severity depending on the specific mutation type. Bone complications, mostly scoliosis but also osteoporosis, hip displacement, and a high rate of fractures, are among the most prevalent non-neurological comorbidities observed in girls with RS. Low bone mineral density (BMD) is primarily due to a slow rate of bone formation due to dysfunctional osteoblast activity. The use of anticonvulsants, immobilization, low physical activity, poor nutrition, and inadequate vitamin D intake all significantly hamper skeletal maturation and the accumulation of bone mass in RS girls, making them more susceptible to fragility fractures. In RS patients, the upper and lower limbs are the most common sites for fractures which are due to both a reduced BMD and a diminished bone size. This review summarizes the knowledge on risk factors for fragility fracture in patients with RS and proposes a potential diagnostic and therapeutic pathway to enhance low BMD and mitigate the risk of fragility fractures. In particular, this review focused on the importance of clinical and instrumental evaluation of bone status as a basis for adequate planning of nutritional, pharmacological, and surgical interventions to be undertaken. Additionally, the management of bone defects in individuals with RS should be customized to meet each person's specific needs, abilities, and general health.

Gastrointestinal manifestations of Rett syndrome: An updated analysis using the Gastrointestinal Health Questionnaire

OBJECTIVE

We conducted a nationwide survey using a validated Gastrointestinal Health Questionnaire (GHQ) for Rett syndrome (RTT) to provide an updated and accurate baseline assessment of the prevalence of common gastrointestinal (GI) issues in RTT, based on parental reporting.

METHODS

Parents and caregivers of females with RTT or normally developing, unaffected, age-matched controls completed the GHQ survey. The prevalence of GI symptoms and personality and mood symptoms due to stomach or intestinal problems, as well as GI medication usage and surgical interventions, were assessed in females with RTT and unaffected controls. The relation between GI symptoms and medication usage, surgical status, age, and genetic mutation were analyzed.

RESULTS

Parents of 118 females with RTT and 27 unaffected females completed the GHQ. GI symptoms were common in females with RTT, including constipation (81%), gas and bloating (70%), issues with eating, chewing and swallowing (73%), and irritability because of stomach or intestinal problems (53%). Females with RTT commonly used proton pump inhibitors (52%) and laxatives (64%). Medication usage was associated with significantly higher GHQ symptom scores. Parents of individuals with RTT reported a significantly higher prevalence of GI symptoms affecting their daughters in all symptom categories compared with unaffected females.

CONCLUSIONS

GI problems are common in RTT and pose a significant medical burden to caregivers. The GHQ is a useful tool to assess GI issues in individuals with RTT. Improved recognition of these issues may allow for improved treatment and enhanced quality of life for girls and women affected by RTT.

The sleep problems in individuals with Rett syndrome and their caregivers

LAY ABSTRACT

Sleep problems are common and impactful among individuals with Rett syndrome (RTT) and their caregivers. We examined the sleep patterns of 29 RTT patients and their primary caregivers using various assessment tools. The study found that a majority of the patients experienced sleep disturbances, with younger patients showing more sleep difficulties. Caregivers also reported poor sleep quality. The findings emphasize the need to address sleep problems in RTT management, as improving sleep quality can positively impact the well-being of individuals with RTT and their caregivers.

Rett syndrome

Rett syndrome (RTT) is a severe, progressive, neurodevelopmental disorder, which affects predominantly females. In most cases, RTT is associated with pathogenic variants in MECP2. MeCP2, the protein product of MECP2, is known to regulate gene expression and is highly expressed in the brain. RTT is characterized by developmental regression of spoken language and hand use that, with hand stereotypies and impaired ambulation, constitute the four core diagnostic features. Affected individuals may present multiple other neurological impairments and comorbidities, such as seizures, breathing irregularities, anxiety and constipation. Studies employing neuroimaging, neuropathology, neurochemistry and animal models show reductions in brain size and global decreases in neuronal size, as well as alterations in multiple neurotransmitter systems. Management of RTT is mainly focused on preventing the progression of symptoms, currently improved by guidelines based on natural history studies. Animal and cellular models of MeCP2 deficiency have helped in understanding the pathophysiology of RTT and guided the development of trofinetide, an IGF1-related compound, which is an approved drug for RTT, as well as of other drugs and gene therapies currently under investigation.

Rett Syndrome: The Emerging Landscape of Treatment Strategies

Rett syndrome (RTT) has enjoyed remarkable progress in achieving specific therapies. RTT, a unique neurodevelopmental disorder first described in 1966, progressed slowly until the landmark paper of Hagberg and colleagues in 1983. Thereafter, rapid advances were achieved including the development of specific diagnostic criteria and the active search for a genetic etiology, resulting 16 years later in identification of variants in the methyl-CpG-binding protein (MECP2) gene located at Xq28. Shortly thereafter, the NIH Office of Rare Diseases funded the RTT Natural History Study (NHS) in 2003, initiating the acquisition of natural history data on clinical features from a large population of individuals with RTT. This information was essential for advancement of clinical trials to provide specific therapies for this disorder. In the process, the International Rett Syndrome Association (IRSA) was formed (now the International Rett Syndrome Foundation-IRSF), which participated directly in encouraging and expanding enrollment in the NHS and, subsequently, in developing the SCOUT program to facilitate testing of potential therapeutic agents in a mouse model of RTT. The overall objective was to review clinical characteristics developed from the NHS and to discuss the status of specific therapies for this progressive neurodevelopmental disorder. The NHS study provided critical information on RTT: growth, anthropometrics, longevity, key comorbidities including epilepsy, breath abnormalities, gastroesophageal dysfunction, scoliosis and other orthopedic issues, puberty, behavior and anxiety, and progressive motor deterioration including the appearance of parkinsonian features. Phenotype-genotype correlations were noted including the role of X chromosome inactivation. Development of clinical severity and quality of life measures also proved critical for subsequent clinical trials. Further, development of biochemical and neurophysiologic biomarkers offered further endpoints for clinical trials. Initial clinical trials prior to the NHS were ineffective, but advances resulting from the NHS and other studies worldwide promoted significant interest from pharmaceutical firms resulting in several clinical trials. While some of these have been unrewarding such as sarizotan, others have been quite promising including the approval of trofinetide by the FDA in 2023 as the first agent available for specific treatment of RTT. Blarcamesine has been trialed in phase 3 trials, 14 agents have been studied in phase 2 trials, and 7 agents are being evaluated in preclinical/translational studies. A landmark study in 2007 by Guy et al. demonstrated that activation of a normal MECP2 gene in a null mouse model resulted in significant improvement. Gene replacement therapy has advanced through translational studies to two current phase 1/2 clinical trials (Taysha102 and Neurogene-401). Additional genetic therapies are also under study including gene editing, RNA editing, and X-chromosome reactivation. Taken together, progress in understanding and treating RTT over the past 40 years has been remarkable. This suggests that further advances can be expected.

Endocrine disorders in Rett syndrome: a systematic review of the literature

Background

Rett syndrome (RTT) is an X-linked progressive neurodevelopmental disorder that involves mainly girls and is the second most frequent cause of genetic intellectual disability. RTT leads to neurological regression between 6 and 18 months of life and could be associated with a variable neurological impairment. However, RTT affects not only neurological function but also wide aspects of non-neurological organs. Recent data showed that the endocrine system is often involved in RTT patients, including disorders of growth, bone health, thyroid, puberty onset, and weight abnormalities However, systematic data on endocrinopathies in RTT are scarce and limited.

Objective

This review aims to analyze the prevalence and type of endocrine comorbidities in RTT population, to allow a precocious diagnosis and appropriate endocrinological management.

Methods

Systematic research was carried out from January 2000 to March 2024 through MEDLINE via PubMed, Scopus, and the Cochrane Library.

Results

After the selection phase, a total of 22 studies (1090 screened) met the inclusion criteria and were reported in the present review. Five studies were observational-retrospective, four were cross-sectional and case report or series, three were survey, prospective, and case-control, and finally one study for descriptive-transversal and longitudinal population-based study. The sample population consisted of multiethnic groups or single ethnic groups. The main endocrinopathies reported were malnutrition, bone alterations, and alterations of puberty onset.

Conclusions

Our analysis shows that endocrinopathies are not rare in RTT patients. Therefore, in the context of a multidisciplinary approach, accurate screening and monitoring for endocrinopathies should be recommended in all RTT patients, to improve clinical practice, healthcare management, and, finally, patients' quality of life.

Comprehensive High-Depth Proteomic Analysis of Plasma Extracellular Vesicles Containing Preparations in Rett Syndrome

Backgroud: Rett syndrome is a neurodevelopmental disorder that affects 1 in 10,000 females. Various treatments have been explored; however, no effective treatments have been reported to date, except for trofinetide, a synthetic analog of glycine-proline-glutamic acid, which was approved by the FDA in 2023. Serological biomarkers that correlate with the disease status of RTT are needed to promote early diagnosis and to develop novel agents. Methods: In this study, we performed a high-depth proteomic analysis of extracellular vesicles containing preparations extracted from patient plasma samples to identify novel biomarkers. Results: We identified 33 upregulated and 17 downregulated candidate proteins among a total of 4273 proteins in RTT compared to the healthy controls. Among these, UBE3B was predominantly increased in patients with Rett syndrome and exhibited a strong correlation with the clinical severity score, indicating the severity of the disease. Conclusions: We demonstrated that the proteomics of high-depth extracellular vesicles containing preparations in rare diseases could be valuable in identifying new disease biomarkers and understanding their pathophysiology.

Nutritional and gastrointestinal manifestations in Rett syndrome: long-term follow-up

PURPOSE

Rett syndrome is a rare neurodevelopmental disorder associated with methyl CpG binding protein 2 (MECP2) gene mutations. We aimed to characterize the long-term nutritional and gastrointestinal course of Rett syndrome in a large national patient population.

METHODS

We conducted a retrospective cohort study of patients followed during 1991-2021 at a national center for Rett syndrome. The data retrieved included clinical features, laboratory and genetic analyses. Continuous anthropometric measurements were calculated for the closest visit to the median ages: 2.5, 7.5, 12.5 and 17.5 years. Kaplan Meier curves were used to describe the appearance of clinical manifestations during the follow up period. Generalized estimating equation models were used to compare repeated measurements.

RESULTS

Included were 141 patients (139 females), the median age at the first visit was 3.2 years (interquartile range [IQR] 2.3-5.7), and the median length of follow-up was 94.5 months (IQR 28.6-153.3). Mean weight, height and BMI Z-scores were -1.09, -1.03 and -0.56, respectively, at median age 2.5 years; and deteriorated to -3.95, -3.01 and -1.19, respectively, at median age 17.5 years (P < 0.001). Gastrointestinal features included constipation (47.5%, 67/141) and chewing/feeding difficulties (20%, 28/141) at presentation; and an additional 47 (33.3%) and 24 (17.0%), respectively, during follow up. Twenty-eight patients (20%) developed aerophagia and 44 (31.2%) gastroesophageal reflux. No relation was found between genetic mutation types and clinical manifestations. GI manifestations were more prevalent in patients with typical form of Rett syndrome.

CONCLUSIONS

Anthropometric parameters were shown to deteriorate with age, regardless of the specific genetic mutation. Chewing/feeding difficulties, constipation and gastroesophageal reflux are common in Rett patients.

24-h continuous non-invasive multiparameter home monitoring of vitals in patients with Rett syndrome by an innovative wearable technology: evidence of an overlooked chronic fatigue status

Background

Sleep is disturbed in Rett syndrome (RTT), a rare and progressive neurodevelopmental disorder primarily affecting female patients (prevalence 7.1/100,000 female patients) linked to pathogenic variations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Autonomic nervous system dysfunction with a predominance of the sympathetic nervous system (SNS) over the parasympathetic nervous system (PSNS) is reported in RTT, along with exercise fatigue and increased sudden death risk. The aim of the present study was to test the feasibility of a continuous 24 h non-invasive home monitoring of the biological vitals (biovitals) by an innovative wearable sensor device in pediatric and adolescent/adult RTT patients.

Methods

A total of 10 female patients (mean age 18.3 ± 9.4 years, range 4.7-35.5 years) with typical RTT and MECP2 pathogenic variations were enrolled. Clinical severity was assessed by validated scales. Heart rate (HR), respiratory rate (RR), and skin temperature (SkT) were monitored by the YouCare Wearable Medical Device (Accyourate Group SpA, L'Aquila, Italy). The average percentage of maximum HR (HRmax%) was calculated. Heart rate variability (HRV) was expressed by consolidated time-domain and frequency-domain parameters. The HR/LF (low frequency) ratio, indicating SNS activation under dynamic exercise, was calculated. Simultaneous continuous measurement of indoor air quality variables was performed and the patients' contributions to the surrounding water vapor partial pressure [PH2O (pt)] and carbon dioxide [PCO2 (pt)] were indirectly estimated.

Results

Of the 6,559.79 h of biovital recordings, 5051.03 h (77%) were valid for data interpretation. Sleep and wake hours were 9.0 ± 1.1 h and 14.9 ± 1.1 h, respectively. HRmax % [median: 71.86% (interquartile range 61.03-82%)] and HR/LF [median: 3.75 (interquartile range 3.19-5.05)] were elevated, independent from the wake-sleep cycle. The majority of HRV time- and frequency-domain parameters were significantly higher in the pediatric patients (p ≤ 0.031). The HRV HR/LF ratio was associated with phenotype severity, disease progression, clinical sleep disorder, subclinical hypoxia, and electroencephalographic observations of multifocal epileptic activity and general background slowing.

Conclusion

Our findings indicate the feasibility of a continuous 24-h non-invasive home monitoring of biovital parameters in RTT. Moreover, for the first time, HRmax% and the HR/LF ratio were identified as potential objective markers of fatigue, illness severity, and disease progression.

Growth patterns in individuals with CDKL5 deficiency disorder

AIM

To compare growth in individuals with cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder with population norms and to investigate the effect of gastrostomy on growth.

METHOD

The longitudinal study included 353 individuals from the International CDKL5 Disorder Database with any anthropometric measurement in baseline and/or follow-up questionnaires. The British 1990 growth reference was used to determine the age- and sex-standardized z-score. Repeated cross-sectional data were fitted using a Gaussian linear regression model with generalized estimating equations.

RESULTS

All growth parameters were below the general population norm (mean z-scores: weight -0.97, height -0.65, body mass index [BMI] -0.81, head circumference -2.12). The disparity was particularly pronounced for all anthropometric measurements after 4 years of age except for BMI. Moreover, individuals with gastrostomy placement were shown to have a larger decrease than those without.

INTERPRETATION

In addition to weight, height, and BMI, head circumference was also compromised in this disorder. Microcephaly could be considered a helpful diagnostic feature, especially in adults. Any benefit of gastrostomy on weight and BMI was mainly seen in the early years.

Prevalence of Endocrinopathies in a Cohort of Patients with Rett Syndrome: A Two-Center Observational Study

Systematic data on endocrinopathies in Rett syndrome (RTT) patients remain limited and inconclusive. The aim of this retrospective observational two-center study was to assess the prevalence of endocrinopathies in a pediatric population of RTT patients. A total of 51 Caucasian patients (47 girls, 4 boys) with a genetically confirmed diagnosis of RTT were enrolled (mean age 9.65 ± 5.9 years). The patients were referred from the Rett Center of two Italian Hospitals for endocrinological evaluation. All the study population underwent clinical and auxological assessments and hormonal workups. MeCP2 mutations were detected in 38 cases (74.5%), CDKL5 deletions in 11 (21.6%), and FOXG1 mutations in 2 (3.9%). Overall, 40 patients were treated with anti-seizure medications. The most frequent endocrinological finding was short stature (47%), followed by menstrual cycle abnormalities (46.2%), weight disorders (45.1%), low bone mineral density (19.6%), hyperprolactinemia (13.7%) and thyroid disorders (9.8%). In the entire study population, endocrinopathies were significantly more frequent in patients with MeCP2 mutations (p = 0.0005), and epilepsy was more frequent in CDKL5 deletions (p = 0.02). In conclusion, our data highlighted that endocrinopathies are not rare in RTT, especially in patients with MeCP2 deletions. Therefore, in the context of a multidisciplinary approach, endocrinological evaluation should be recommended for RTT patients.

Growth disorders caused by variants in epigenetic regulators: progress and prospects

Epigenetic modifications play an important role in regulation of transcription and gene expression. The molecular machinery governing epigenetic modifications, also known as epigenetic regulators, include non-coding RNA, chromatin remodelers, and enzymes or proteins responsible for binding, reading, writing and erasing DNA and histone modifications. Recent advancement in human genetics and high throughput sequencing technology have allowed the identification of causative variants, many of which are epigenetic regulators, for a wide variety of childhood growth disorders that include skeletal dysplasias, idiopathic short stature, and generalized overgrowth syndromes. In this review, we highlight the connection between epigenetic modifications, genetic variants in epigenetic regulators and childhood growth disorders being established over the past decade, discuss their insights into skeletal biology, and the potential of epidrugs as a new type of therapeutic intervention.

Rett syndrome in Ireland: a demographic study

BACKGROUND

Rett syndrome (RTT) is a rare neurodevelopmental condition associated with mutations in the gene coding for the methyl-CpG-binding protein 2 (MECP2). It is primarily observed in girls and affects individuals globally. The understanding of the neurobiology of RTT and patient management has been improved by studies that describe the demographic and clinical presentation of individuals with RTT. However, in Ireland, there is a scarcity of data regarding individuals with RTT, which impedes the ability to fully characterize the Irish RTT population. Together with the Rett Syndrome Association of Ireland (RSAI), we prepared a questionnaire to determine the characteristics of RTT individuals in Ireland. Twenty-five families have participated in the study to date, providing information about demographics, genetics, familial history, clinical features, and regression.

RESULTS

The results show that Irish individuals with RTT have comparable presentation with respect to individuals in other countries; however, they had a better response to anti-epileptic drugs, and fewer skeletal deformities were reported. Nonetheless, seizures, involuntary movements and regression were more frequently observed in Irish individuals. One of the main findings of this study is the limited genetic information available to individuals to support the clinical diagnosis of RTT.

CONCLUSIONS

Despite the limited sample size, this study is the first to characterize the RTT population in Ireland and highlights the importance of having a swift access to genetic testing to sharpen the characterization of the phenotype and increase the visibility of Irish individuals in the international RTT community.

Rett Syndrome and the Role of MECP2: Signaling to Clinical Trials

Rett syndrome (RTT) is a neurological disorder that mostly affects females, with a frequency of 1 in 10,000 to 20,000 live birth cases. Symptoms include stereotyped hand movements; impaired learning, language, and communication skills; sudden loss of speech; reduced lifespan; retarded growth; disturbance of sleep and breathing; seizures; autism; and gait apraxia. Pneumonia is the most common cause of death for patients with Rett syndrome, with a survival rate of 77.8% at 25 years of age. Survival into the fifth decade is typical in Rett syndrome, and the leading cause of death is cardiorespiratory compromise. Rett syndrome progression has multiple stages; however, most phenotypes are associated with the nervous system and brain. In total, 95% of Rett syndrome cases are due to mutations in the MECP2 gene, an X-linked gene that encodes for the methyl CpG binding protein, a regulator of gene expression. In this review, we summarize the recent developments in the field of Rett syndrome and therapeutics targeting MECP2.

A novel pathogenic mutation of MeCP2 impairs chromatin association independent of protein levels

Loss-of-function mutations in MECP2 cause Rett syndrome (RTT), a severe neurological disorder that mainly affects girls. Mutations in MECP2 do occur in males occasionally and typically cause severe encephalopathy and premature lethality. Recently, we identified a missense mutation (c.353G>A, p.Gly118Glu [G118E]), which has never been seen before in MECP2, in a young boy who suffered from progressive motor dysfunction and developmental delay. To determine whether this variant caused the clinical symptoms and study its functional consequences, we established two disease models, including human neurons from patient-derived iPSCs and a knock-in mouse line. G118E mutation partially reduces MeCP2 abundance and its DNA binding, and G118E mice manifest RTT-like symptoms seen in the patient, affirming the pathogenicity of this mutation. Using live-cell and single-molecule imaging, we found that G118E mutation alters MeCP2's chromatin interaction properties in live neurons independently of its effect on protein levels. Here we report the generation and characterization of RTT models of a male hypomorphic variant and reveal new insight into the mechanism by which this pathological mutation affects MeCP2's chromatin dynamics. Our ability to quantify protein dynamics in disease models lays the foundation for harnessing high-resolution single-molecule imaging as the next frontier for developing innovative therapies for RTT and other diseases.

Natural Course of IQSEC2-Related Encephalopathy: An Italian National Structured Survey

Pathogenic loss-of-function variants in the IQ motif and SEC7 domain containing protein 2 (IQSEC2) gene cause intellectual disability with Rett syndrome (RTT)-like features. The aim of this study was to obtain systematic information on the natural history and extra-central nervous system (CNS) manifestations for the Italian IQSEC2 population (>90%) by using structured family interviews and semi-quantitative questionnaires. IQSEC2 encephalopathy prevalence estimate was 7.0 to 7.9 × 10-7. Criteria for typical RTT were met in 42.1% of the cases, although psychomotor regression was occasionally evidenced. Genetic diagnosis was occasionally achieved in infancy despite a clinical onset before the first 24 months of life. High severity in both the CNS and extra-CNS manifestations for the IQSEC2 patients was documented and related to a consistently adverse quality of life. Neurodevelopmental delay was diagnosed before the onset of epilepsy by 1.8 to 2.4 years. An earlier age at menarche in IQSEC2 female patients was reported. Sleep disturbance was highly prevalent (60 to 77.8%), with mandatory co-sleeping behavior (50% of the female patients) being related to de novo variant origin, younger age, taller height with underweight, better social interaction, and lower life quality impact for the family and friends area. In conclusion, the IQSEC2 encephalopathy is a rare and likely underdiagnosed developmental encephalopathy leading to an adverse life quality impact.

Multidisciplinary Management of Rett Syndrome: Twenty Years' Experience

Over the last 20 years, the understanding and natural history of Rett syndrome has advanced, but to date no cure has emerged, with multidisciplinary management being symptomatic and supportive. This study provides a comprehensive review of the clinical features, comorbidities and multidisciplinary management of a well-characterized cohort of females with classical Rett syndrome. We aim to improve awareness and understanding of Rett syndrome amongst pediatricians, pediatric subspecialists and allied health professionals to enable early diagnosis and a streamlined enrolment approach for future clinical trials. Rett syndrome, a complex X-linked condition, affecting mainly females, is due to pathogenic variants of the MECP2 gene in most affected individuals. The Rett syndrome Multidisciplinary Management clinic at The Children's Hospital at Westmead, Sydney, Australia, was established in 2000. This retrospective analysis of individuals who attended the clinic from 2000 to 2020 was performed to identify the incidence and predicted age of onset of Rett syndrome related comorbidities, disease progression and to review management principles. Data collected included age of Rett syndrome diagnosis, MECP2 genotype, clinical features and medical comorbidities, such as sleep disturbance, seizures, breathing irregularities, scoliosis, mobility, hand stereotypies, hand function, constipation, feeding ability, use of gastrostomy, communication skills, QTc prolongation, anthropometry, and bruxism. Analysis of 103 girls who fulfilled the clinical diagnostic criteria for classical Rett syndrome with a pathogenic variant of the MECP2 gene showed a median age of diagnosis of 3 years. The most frequent MECP2 variant was c.502 C>T.

Exploring gastrointestinal health in MECP2 duplication syndrome

BACKGROUND

MECP2 duplication syndrome (MDS) is a rare neurogenetic syndrome caused by duplications of MECP2 at the Xq28 region. Although constipation and gastrointestinal reflux are reported in MDS, a comprehensive characterization of gastrointestinal health has not been fully explored.

METHODS

We conducted a parent survey to explore the characteristics of gastrointestinal health in individuals with MDS using a secure online registry and compared differences in gastrointestinal symptoms between individuals with MDS and those with Rett syndrome (RTT).

KEY RESULTS

One hundred six surveys were analyzed. Symptoms commonly associated with constipation occurred in 72% to 89% of MDS individuals. Eleven percent of MDS individuals underwent surgery for complications associated with constipation. We observed a bimodal distribution for gastroesophageal reflux disease (GERD) and gastrostomy feeding, with higher prevalence in 0-3 and >12-year-old MDS individuals. Constipation and GERD were significantly more common, and gas bloating was significantly less common in MDS than in RTT. Biliary tract disease requiring surgery was an unrecognized problem in 5% of MDS individuals. We determined that gastrointestinal problems in MDS individuals contribute to caretaker burden.

CONCLUSION AND INFERENCES

Our study is the first in-depth investigation that characterizes gastrointestinal health in MDS and enumerates differences in gastrointestinal symptoms between MDS and RTT. Strategies to reduce gastrointestinal symptoms will alleviate caregiver burden in MDS. Further studies are needed to examine the mechanisms that cause gastrointestinal problems in MDS.

A narrative review of the mechanisms and consequences of intermittent hypoxia and the role of advanced analytic techniques in pediatric autonomic disorders

Disorders of autonomic functions are typically characterized by disturbances in multiple organ systems. These disturbances are often comorbidities of common and rare diseases, such as epilepsy, sleep apnea, Rett syndrome, congenital heart disease or mitochondrial diseases. Characteristic of many autonomic disorders is the association with intermittent hypoxia and oxidative stress, which can cause or exaggerate a variety of other autonomic dysfunctions, making the treatment and management of these syndromes very complex. In this review we discuss the cellular mechanisms by which intermittent hypoxia can trigger a cascade of molecular, cellular and network events that result in the dysregulation of multiple organ systems. We also describe the importance of computational approaches, artificial intelligence and the analysis of big data to better characterize and recognize the interconnectedness of the various autonomic and non-autonomic symptoms. These techniques can lead to a better understanding of the progression of autonomic disorders, ultimately resulting in better care and management.

The Rare Diseases Clinical Research Network: a model for clinical trial readiness

Background

The current road to developing treatments for rare diseases is often slow, expensive, and riddled with risk. Change is needed to improve the process, both in how we think about rare disease treatment development and the infrastructure we build to support ongoing science. The National Institutes of Health (NIH)-supported Rare Diseases Clinical Research Network (RDCRN) was established to advance the diagnosis, management, and treatment of rare diseases and to promote highly collaborative, multi-site, patient-centric, translational, and clinical research. The current iteration of the RDCRN intends to build upon and enhance successful approaches within the network while identifying innovative methods to fill gaps and address needs in the approach to the rare disease treatment development process through innovation, collaboration, and clinical trial readiness.

Objective

The objective of this paper is to provide an overview of the productivity and influence of the RDCRN since it was first established 20 years ago.

Design and methods

Using a suite of tools available to NIH staff that provides access to a comprehensive, curated, extensively linked data set of global grants, patents, publications, clinical trials, and FDA-approved drugs, a series of queries were executed that conducted bibliometric, co-author, and co-occurrence analysis.

Results

The results demonstrate that the entire RDCRN consortia and network has been highly productive since its inception. They have produced 2763 high-quality publications that have been cited more than 100,000 times, expanded international networks, and contributed scientifically to eight FDA-approved treatments for rare diseases.

Conclusion

The RDCRN program has successfully addressed some significant challenges while developing treatments for rare diseases. However, looking to the future and being agile in facing new challenges that arise as science progresses is important.

Early life stress exacerbates behavioural and neuronal alterations in adolescent male mice lacking methyl-CpG binding protein 2 (Mecp2)

The methyl-CpG binding protein 2 gene (MECP2) encodes an epigenetic transcriptional regulator implicated in neuronal plasticity. Loss-of-function mutations in this gene are the primary cause of Rett syndrome and, to a lesser degree, of other neurodevelopmental disorders. Recently, we demonstrated that both Mecp2 haploinsuficiency and mild early life stress decrease anxiety-like behaviours and neuronal activation in brain areas controlling these responses in adolescent female mice. Here, we extend this work to males by using Mecp2-null and wild type adolescent mice subjected to maternal separation and their non-stressed controls. We assessed their behavioural responses in a battery of anxiety-provoking tests. Upon exposure to an elevated plus maze in aversive conditions, we evaluated changes in c-FOS expression in stress- and anxiety-related brain regions. In addition, we assessed the impact of maternal separation in neuronal maturation using doublecortin and reelin as surrogate markers. Mutant males showed reduced motor abilities, increased activation of the olfactory bulbs, probably due to breathing abnormalities, and decreased activation of the paraventricular thalamic nucleus, when compared to wild type mice. In addition, maternal separation increased the number of immature doublecortin-like neurons found in Mecp2-null animals. Moreover, this work shows for the first time that reelin is decreased in the mutant animals at the olfactory tubercle, piriform cortex and hippocampal dentate gyrus, an effect also associated to maternal separation. Taken together, our results suggest that maternal separation exacerbates some phenotypical alterations associated with lack of MeCP2 in adolescent males.

The Role of Genetics in Central Precocious Puberty: Confirmed and Potential Neuroendocrine Genetic and Epigenetic Contributors and Their Interactions with Endocrine Disrupting Chemicals (EDCs)

Despite the growing prevalence of central precocious puberty (CPP), most cases are still diagnosed as “idiopathic” due to the lack of identifiable findings of other diagnostic etiology. We are gaining greater insight into some key genes affecting neurotransmitters and receptors and how they stimulate or inhibit gonadotropin-releasing hormone (GnRH) secretion, as well as transcriptional and epigenetic influences. Although the genetic contributions to pubertal regulation are more established in the hypogonadotropic hypogonadism (HH) literature, cases of CPP have provided the opportunity to learn more about its own genetic influences. There have been clinically confirmed cases of CPP associated with gene mutations in kisspeptin and its receptor (KISS1, KISS1R), Delta-like noncanonical Notch ligand 1 (DLK1), and the now most commonly identified genetic cause of CPP, makorin ring finger protein (MKRN3). In addition to these proven genetic causes, a number of other candidates continue to be evaluated. After reviewing the basic clinical aspects of puberty, we summarize what is known about the various genetic and epigenetic causes of CPP as well as discuss some of the potential effects of endocrine disrupting chemicals (EDCs) on some of these processes.

Anthropometric Measures Correspond with Functional Motor Outcomes in Females with Rett Syndrome

OBJECTIVE

To characterize growth and anthropometric measurements in females with Rett syndrome and compare these measurements with functional outcomes.

STUDY DESIGN

We obtained longitudinal growth and anthropometric measurements from 1154 females with classic and atypical Rett syndrome seen between 2006 and 2019 in the US Natural History Study. We calculated the Clinical Severity Score, Motor Behavior Assessment score, and arm and leg muscle areas and recorded the functional assessments of arm and hand use and ambulation. We compared growth and anthropometric variables from females with Rett syndrome in regard to normative data. We analyzed Clinical Severity Score, Motor Behavior Assessment, and anthropometric measurements in regard to functional assessments.

RESULTS

Growth and anthropometric measurements were significantly lower in females with classic and severe atypical Rett syndrome compared with those classified as mild atypical Rett syndrome and deviated from normative patterns among all 3 groups. Suprailiac skinfold measurements correlated with body mass index measurements in each group. Lower leg muscle area measurements were significantly greater among females in all 3 Rett syndrome groups who ambulated independently compared with those who did not. In females with classic Rett syndrome, arm, thigh, and lower leg muscle area measurements increased significantly over time and were significantly greater among those who had purposeful arm and hand use and independent ambulation compared with those who did not.

CONCLUSIONS

The pattern of growth and anthropometric measures in females with Rett syndrome differs from normative data and demonstrates clear differences between classic and mild or severe atypical Rett syndrome. Anthropometric measures correspond with functional outcomes and could provide markers supporting efficacy outcomes in clinical trials.

Breathing Abnormalities During Sleep and Wakefulness in Rett Syndrome: Clinical Relevance and Paradoxical Relationship With Circulating Pro-oxidant Markers

Background

Breathing abnormalities are common in Rett syndrome (RTT), a pervasive neurodevelopmental disorder almost exclusively affecting females. RTT is linked to mutations in the methyl-CpG-binding protein 2 (MeCP2) gene. Our aim was to assess the clinical relevance of apneas during sleep-wakefulness cycle in a population with RTT and the possible impact of apneas on circulating oxidative stress markers.

Methods

Female patients with a clinical diagnosis of typical RTT (n = 66), MECP2 gene mutation, and apneas were enrolled (mean age: 12.5 years). Baseline clinical severity, arterial blood gas analysis, and red blood cell count were assessed. Breathing was monitored during the wakefulness and sleep states (average recording time: 13 ± 0.5 h) with a portable polygraphic screening device. According to prevalence of breath holdings, the population was categorized into the wakefulness apnea (WA) and sleep apnea (SA) groups, and apnea-hypopnea index (AHI) was calculated. The impact of respiratory events on oxidative stress was assessed by plasma and intra-erythrocyte non-protein-bound iron (P-NPBI and IE-NPBI, respectively), and plasma F2-isoprostane (F2-IsoP) assays.

Results

Significant prevalence of obstructive apneas with values of AHI &gt; 15 was present in 69.7% of the population with RTT. The group with SA showed significantly increased AHI values &gt; 15 (p = 0.0032), total breath holding episodes (p = 0.007), and average SpO2 (p = 0.0001) as well as lower nadir SpO2 (p = 0.0004) compared with the patients with WAs. The subgroups of patients with WA and SA showed no significant differences in arterial blood gas analysis variables (p &gt; 0.089). Decreased mean cell hemoglobin (MCH) (p = 0.038) was observed in the group with WAs. P-NPBI levels were significantly higher in the group with WA than in that with SAs (p = 0.0001). Stepwise multiple linear regression models showed WA being related to nadir SpO2, average SpO2, and P-NPBI (adjusted R2 = 0.613, multiple correlation coefficient = 0.795 p &lt; 0.0001), and P-NPBI being related to average SpO2, blood PaCO2, red blood cell mean corpuscular volume (MCV), age, and topiramate treatment (adjusted R2 = 0.551, multiple correlation coefficient = 0.765, p &lt; 0.0001).

Conclusion

Our findings indicate that the impact of apneas in RTT is uneven according to the sleep-wakefulness cycle, and that plasma redox active iron represents a potential novel therapeutic target.

Improving clinical trial readiness to accelerate development of new therapeutics for Rett syndrome

Rett syndrome is associated with severe functional impairments and many comorbidities, each in urgent need of treatments. Mutations in the MECP2 gene were identified as causing Rett syndrome in 1999. Over the past 20 years there has been an abundance of preclinical research with some studies leading to human clinical trials. Despite this, few viable therapeutic options have emerged from this investment of effort. Reasons for this lack of success as they relate both to preclinical research and the clinical trial landscape are discussed. Considering what needs to be done to promote further success in the field, we take a positive and constructive approach and introduce the concept of clinical trial readiness and its necessary ingredients for Rett syndrome. These include: listening to the needs of families; support from advocacy groups; optimising use of existing clinic infrastructures and available natural history data; and, finally, the validation of existing outcome measures and/or the development and validation of new measures. We conclude by reiterating the need for a collaborative and coordinated approach amongst the many different stakeholder groups and the need to engage in new types of trial design which could be much more efficient, less costly and much less burdensome on families.

Breathing disturbances in Rett syndrome

Rett Syndrome is an X-linked neurological disorder characterized by behavioral and neurological regression, seizures, motor deficits, and dysautonomia. A particularly prominent presentation includes breathing abnormalities characterized by breathing irregularities, hyperventilation, repetitive breathholding during wakefulness, obstructive and central apneas during sleep, and abnormal responses to hypoxia and hypercapnia. The condition and pathology of the respiratory system is further complicated by dysfunctions of breathing-motor coordination, which is reflected in dysphagia. The discovery of the X-linked mutations in the MECP2 gene has transformed our understanding of the cellular and molecular mechanisms that are at the root of various clinical phenotypes. However, the genotype-phenotype relationship is complicated by various factors which include not only X-inactivation but also consequences of the intermittent hypoxia and oxidative stress associated with the breathing abnormalities.

Post-synaptic scaffold protein TANC2 in psychiatric and somatic disease risk

Understanding the shared genetic aetiology of psychiatric and medical comorbidity in neurodevelopmental disorders (NDDs) could improve patient diagnosis, stratification and treatment options. Rare tetratricopeptide repeat, ankyrin repeat and coiled-coil containing 2 (TANC2)-disrupting variants were disease causing in NDD patients. The post-synaptic scaffold protein TANC2 is essential for dendrite formation in synaptic plasticity and plays an unclarified but critical role in development. We here report a novel homozygous-viable Tanc2-disrupted function model in which mutant mice were hyperactive and had impaired sensorimotor gating consistent with NDD patient psychiatric endophenotypes. Yet, a multi-systemic analysis revealed the pleiotropic effects of Tanc2 outside the brain, such as growth failure and hepatocellular damage. This was associated with aberrant liver function including altered hepatocellular metabolism. Integrative analysis indicates that these disrupted Tanc2 systemic effects relate to interaction with Hippo developmental signalling pathway proteins and will increase the risk for comorbid somatic disease. This highlights how NDD gene pleiotropy can augment medical comorbidity susceptibility, underscoring the benefit of holistic NDD patient diagnosis and treatment for which large-scale preclinical functional genomics can provide complementary pleiotropic gene function information.

Summary: Disruption of mouse Tanc2 causes brain and liver abnormality, increasing psychiatric and somatic disease risk long term, highlighting the benefit of holistic diagnosis and treatment approaches for human neurodevelopmental disorder.

Assessment of the gut bacterial microbiome and metabolome of girls and women with Rett Syndrome

BACKGROUND

Gastrointestinal problems affect the health and quality of life of individuals with Rett syndrome (RTT) and pose a medical hardship for their caregivers. We hypothesized that the variability in the RTT phenotype contributes to the dysbiosis of the gut microbiome and metabolome in RTT, predisposing these individuals to gastrointestinal dysfunction.

OBJECTIVES

We characterized the gut bacterial microbiome and metabolome in girls and young women with RTT (n = 44) and unaffected controls (n = 21), and examined the relation between the composition of the microbiome and variations in the RTT phenotype.

METHODS

Demographics and clinical information, including growth and anthropometric measurements, pubertal status, symptoms, clinical severity score, bowel movement, medication use, and dietary intakes were collected from the participants. Fecal samples were collected for analysis of the gut microbiome using Illumina MiSeq-based next-generation sequencing of the 16S rRNA gene followed by bioinformatics analysis of microbial composition, diversity, and community structure. Selected end-products of microbial protein metabolism were characterized by liquid chromatography-mass spectrometry.

RESULTS

The gut bacterial microbiome differed within the RTT cohort based on pubertal status (p<0.02) and clinical severity scores (p<0.02) of the individuals and the type of diet (p<0.01) consumed. Although the composition of the gut microbiome did not differ between RTT and unaffected individuals, concentrations of protein end-products of the gut bacterial metabolome, including γ-aminobutyric acid (GABA) (p<0.001), tyrosine (p<0.02), and glutamate (p<0.06), were lower in the RTT cohort. Differences in the microbiome within RTT groups, based on symptomatic anxiety, hyperventilation, abdominal distention, or changes in stool frequency and consistency, were not detected.

CONCLUSIONS

Although variability in the RTT phenotype contributes to the dysbiosis of the gut microbiome, we presently cannot infer causality between gut bacterial dysbiosis and gastrointestinal dysfunction. Nevertheless, alterations in the gut metabolome may provide clues to the pathophysiology of gastrointestinal problems in RTT.

Dietary intake and growth deficits in Rett syndrome-A cross-section study

Growth deficit is a common comorbidity and one of the supportive criteria in Rett syndrome (RTT). This study aimed to investigate the impact of dystonia, dietary intakes, and clinical severities on growth patterns in a Taiwanese cohort of RTT. We recruited 44 RTT patients with MECP2 mutation for analysis. For individuals ≤18 years of age, in comparison to the RTT-specific growth chart which comprised American RTT cohort, the body height was right-shifted to a higher percentile, whereas the body weight was left-shifted to a lower percentile. Furthermore, the body mass index was significantly decreased when compared to RTT-specific growth chart (p = 0.01). Higher degree of overall disease severity (odd ratio = 1.159; 95% CI = 1.063-1.264; p = 0.001) and hand use impairment (odd ratio = 2.017; 95% CI = 1.037, 3.921; p = 0.039) were associated with more severe growth patterns. All individuals had dystonia at certain variable degrees. The dystonia worsened with age (p < 0.001) but did not have significant impact on growth deficit. Most of our cohort had adequate protein (97.37%) and energy (58.97%) intakes. The fiber intakes were generally low, with about 38 (97.4%) individuals did not meet the daily reference intakes of fiber. The protein intake was significantly lower in individuals with severe growth deficit (p = 0.04). Our study shows that ethnicity should be considered when comparing RTT individuals' growth pattern to the RTT-specific growth chart. Further, disease severity, genotypes, and nutrition exert important impacts on RTT-growth pattern. LAY SUMMARY: Growth impairment is an important issue in Rett syndrome and the underlying patho-mechanism is multifactorial. Higher degree of overall disease severity and hand use impairment were associated with more severe growth pattern deficits. Although all individuals had dystonia at certain variable degrees and the dystonia worsened with age, but it did not have significant impact on growth deficit. Nutritional intakes may partially affect growth. Furthermore, ethnicity should be considered when comparing RTT individuals' growth pattern to the RTT-specific growth chart.

Gastrointestinal Health Questionnaire for Rett Syndrome: Tool Development

OBJECTIVES

We report the development and validation of a tool to assess gastrointestinal health in Rett syndrome (RTT). We hypothesized that the Gastrointestinal Health Questionnaire (GHQ) is a valid clinical outcomes measure of gastrointestinal health in RTT.

PATIENTS AND METHODS

We used parent interviews, surveys, and literature review to generate a questionnaire related to gastrointestinal health and function, mood and behaviors, and parental concerns for individuals with RTT. Parents of affected and unaffected individuals provided responses to the GHQ, assessed the relevance and importance of statements, and completed 5 surveys related to gastrointestinal health, child-related mood and behaviors, and parent concerns. We used multivariate item analysis, 2-sample t tests, and correlations to assess the validity of the GHQ.

RESULTS

We documented acceptable internal consistency of statements related to gastrointestinal health and function (Cronbach-α = 0.91), RTT-related mood and behaviors (Cronbach-α = 0.89), and parent concerns (Cronbach-α = 0.95) in the GHQ. We documented favorable external validity based on differences in response scores between parents of affected and unaffected individuals (P < 0.001) and correlations in parental response scores between the GHQ and 5 validated questionnaires addressing similar issues (P < 0.001).

CONCLUSION

The GHQ is a valid tool for the assessment of gastrointestinal health in RTT and offers the opportunity to field test the safety and efficacy of novel drug therapies in clinical trials for individuals affected with this disorder.

Unraveling Molecular Pathways Altered in MeCP2-Related Syndromes, in the Search for New Potential Avenues for Therapy

Methyl-CpG-binding protein 2 (MeCP2) is an X-linked epigenetic modulator whose dosage is critical for neural development and function. Loss-of-function mutations in MECP2 cause Rett Syndrome (RTT, OMIM #312750) while duplications in the Xq28 locus containing MECP2 and Interleukin-1 receptor-associated kinase 1 (IRAK1) cause MECP2 duplication syndrome (MDS, OMIM #300260). Both are rare neurodevelopmental disorders that share clinical symptoms, including intellectual disability, loss of speech, hand stereotypies, vasomotor deficits and seizures. The main objective of this exploratory study is to identify novel signaling pathways and potential quantitative biomarkers that could aid early diagnosis and/or the monitoring of disease progression in clinical trials. We analyzed by RT-PCR gene expression in whole blood and microRNA (miRNA) expression in plasma, in a cohort of 20 females with Rett syndrome, 2 males with MECP2 duplication syndrome and 28 healthy controls, and correlated RNA expression with disease and clinical parameters. We have identified a set of potential biomarker panels for RTT diagnostic and disease stratification of patients with microcephaly and vasomotor deficits. Our study sets the basis for larger studies leading to the identification of specific miRNA signatures for early RTT detection, stratification, disease progression and segregation from other neurodevelopmental disorders. Nevertheless, these data will require verification and validation in further studies with larger sample size including a whole range of ages.

Meaningful word acquisition is associated with walking ability over 10 years in Rett syndrome

PURPOSE

To investigate walking ability in Japanese patients with Rett syndrome (RTT).

METHODS

Walking ability was assessed in 100 female Japanese patients with RTT using univariate and multivariate analysis in all age groups, and in patients over 10 years of age. We analyzed walking ability and confounding factors including prenatal-perinatal histories, developmental milestones, somatic and head growth, anthropometric data, body mass index, age of loss of purposeful hand use, age at onset of stereotypic hand movement, history of autistic behavior, age at regression, presence or absence of seizures, and the results of MECP2 genetic examination from the Japanese Rett syndrome database.

RESULTS

Univariate analysis revealed that acquisition of walking in all age groups was significantly correlated with the acquisition of meaningful words, microcephaly, and crawling (P < 0.0001, P = 0.005, P < 0.0001, respectively). Univariate analysis revealed that walking ability over 10 years of age was significantly correlated with acquisition of meaningful words, microcephaly, and body mass index (P < 0,0001, P = 0.005, P = 0.0018, respectively). MECP2 mutations R306C, R133C, and R294X were significantly associated with different acquisition of crawling (P = 0.004) and walking (P = 0.01). Multivariate analysis revealed that only acquisition of meaningful words was significantly correlated with walking ability over 10 years of age. This trend excluded the genetic effects of R306C, R133C, and R294X.

CONCLUSIONS

Meaningful word acquisition was robustly associated with walking ability over 10 years. Prognosis of walking ability may be predicted by the acquisition of meaningful words. This information is potentially useful for early intervention and the planning of comprehensive treatment for young children with RTT.

The Pathophysiology of Rett Syndrome With a Focus on Breathing Dysfunctions

Rett syndrome (RTT), an X-chromosome-linked neurological disorder, is characterized by serious pathophysiology, including breathing and feeding dysfunctions, and alteration of cardiorespiratory coupling, a consequence of multiple interrelated disturbances in the genetic and homeostatic regulation of central and peripheral neuronal networks, redox state, and control of inflammation. Characteristic breath-holds, obstructive sleep apnea, and aerophagia result in intermittent hypoxia, which, combined with mitochondrial dysfunction, causes oxidative stress-an important driver of the clinical presentation of RTT.

Assessment of a Clinical Trial Metric for Rett Syndrome: Critical Analysis of the Rett Syndrome Behavioural Questionnaire

BACKGROUND

Rett syndrome is a neurodevelopmental disorder with potential for improvement through novel targeted therapeutics. Reliable outcome measures are critical to the development of treatments. We examined the merits and flaws of the Rett Syndrome Behavioural Questionnaire, an outcome measure for clinical trials.

METHODS

The Rett Syndrome Behavioural Questionnaire was administered alongside other clinical scales in three cohorts, an online survey, a clinic-based study, and the screening period for a clinical trial. Data were collected from individuals with Rett syndrome and related disorders at three time points, separated by a minimum of one week and a maximum of two months. We hypothesized that for clinical trial use, little change should occur among visits. Distribution statistics, internal consistency, intraclass correlation coefficient, percent agreement, and Cohen's kappa were examined.

RESULTS

Among 149 with classic Rett syndrome, the Rett Syndrome Behavioural Questionnaire was completed 377 times. Median total score was 33, ranging from 3 to 73. Of the 51 items tested in the original Rett Syndrome Behavioural Questionnaire study, 24 exhibited either floor or ceiling effects. Friedman's analysis of variance revealed significant difference among visits (P = 0.024), and graphical analysis using Bland-Altman plots demonstrated systematic positive bias with a 95% confidence interval including up to 12.9 points higher to 15.7 points lower at retest. Median agreement measured by kappa was 0.53 for retest at visit 2 and 0.49 for retest at visit 3.

CONCLUSIONS

The Rett Syndrome Behavioural Questionnaire did not achieve acceptable standards as an outcome assessment for clinical trials in Rett syndrome.

Metabolic Signatures Differentiate Rett Syndrome From Unaffected Siblings

Rett syndrome (RTT, OMIM 312750), a severe neurodevelopmental disorder characterized by regression with loss of spoken language and hand skills, development of characteristic hand stereotypies, and gait dysfunction, is primarily caused by de novo mutations in the X-linked gene Methyl-CpG-binding protein 2 (MECP2). Currently, treatment options are limited to symptomatic management, however, reversal of disease phenotype is possible in mouse models by restoration of normal MECP2 gene expression. A significant challenge is the lack of biomarkers of disease state, disease severity, or treatment response. Using a non-targeted metabolomic approach we evaluated metabolite profiles in plasma from thirty-four people with RTT compared to thirty-seven unaffected age- and gender-matched siblings. We identified sixty-six significantly altered metabolites that cluster broadly into amino acid, nitrogen handling, and exogenous substance pathways. RTT disease metabolite and metabolic pathways abnormalities point to evidence of oxidative stress, mitochondrial dysfunction, and alterations in gut microflora. These observed changes provide insight into underlying pathological mechanisms and the foundation for biomarker discovery of disease severity biomarkers.

Consensus guidelines on managing Rett syndrome across the lifespan

BACKGROUND

Rett syndrome (RTT) is a severe neurodevelopmental disorder with complex medical comorbidities extending beyond the nervous system requiring the attention of health professionals. There is no peer-reviewed, consensus-based therapeutic guidance to care in RTT. The objective was to provide consensus on guidance of best practice for addressing these concerns.

METHODS

Informed by the literature and using a modified Delphi approach, a consensus process was used to develop guidance for care in RTT by health professionals.

RESULTS

Typical RTT presents early in childhood in a clinically recognisable fashion. Multisystem comorbidities evolve throughout the lifespan requiring coordination of care between primary care and often multiple subspecialty providers. To assist health professionals and families in seeking best practice, a checklist and detailed references for guidance were developed by consensus.

CONCLUSIONS

The overall multisystem issues of RTT require primary care providers and other health professionals to manage complex medical comorbidities within the context of the whole individual and family. Given the median life expectancy well into the sixth decade, guidance is provided to health professionals to achieve current best possible outcomes for these special-needs individuals.

Caregiver- and Clinician-Reported Adaptive Functioning in Rett Syndrome: a Systematic Review and Evaluation of Measurement Strategies

Rett syndrome is the second most common cause of intellectual disability in females worldwide. The severity of many individuals' impairment limits the effectiveness of traditional assessment. However, clinician and parent reports of adaptive functioning may provide insight into these patients' abilities. This review aims to synthesize the current literature assessing adaptive functioning in Rett syndrome and evaluate existing measurement tools in this population. A search was conducted on PubMed using the search term "Rett syndrome." Studies that quantitatively assessed adaptive functioning outcomes in Rett syndrome with published and normed questionnaire measures were included. Twenty-three studies met inclusion criteria. Overall results indicate that the population of people with Rett syndrome is highly impaired, both in overall adaptive functioning as well as in specific subdomains (e.g., mobility, activities of daily living). Atypical Rett syndrome groups performed better on measures of adaptive functioning relative to patients with classic Rett syndrome. Our findings identified measurement weaknesses, as many of the studies found floor effects and therefore were unable to capture meaningful variability in outcomes. Individuals with Rett syndrome are highly reliant on caregivers due to disrupted adaptive functioning abilities. Optimizing measurement of adaptive skills in Rett syndrome will facilitate the quantification of meaningful change in skills and the identification of efficacious interventions aimed at improving outcomes and quality of life.

A New Scale to Evaluate Motor Function in Rett Syndrome: Validation and Psychometric Properties

BACKGROUND

We aim to describe and psychometrically validate the Rett Syndrome Motor Evaluation Scale, a 25-item ordinal scale examining (loco-)motor function across six sections: standing, sitting, transitions, walking, running, and walking up or downstairs.

METHODS

We illustrate the process of item construction and validation, report findings and normative data obtained on a standardization sample of 60 patients with Rett syndrome. We investigate the validity and reliability of the scale and illustrate its psychometric properties using modern multivariate techniques of data analysis.

RESULTS

Sixty patients with Rett syndrome were included (all female; mean age 12.45 (S.D. 8.75) years). The multidimensional latent structure of the scale was supported by the results of the confirmatory factor analysis. Rett Syndrome Motor Evaluation Scale showed strong internal consistency reliability as well as excellent inter-rater agreement. The Rett Syndrome Motor Evaluation Scale scores were not predicted by age, but were associated with disease severity, degree of spasticity, and hand dysfunction. We also identified three latent classes with different degrees of impairment.

CONCLUSIONS

Rett Syndrome Motor Evaluation Scale is a new, valid, and reliable scale that can be introduced in clinical practice when assessing (loco-)motor function in Rett syndrome.

Molecular Systems Biology of Neurodevelopmental Disorders, Rett Syndrome as an Archetype

Neurodevelopmental disorders represent a challenging biological and medical problem due to their genetic and phenotypic complexity. In many cases, we lack the comprehensive understanding of disease mechanisms necessary for targeted therapeutic development. One key component that could improve both mechanistic understanding and clinical trial design is reliable molecular biomarkers. Presently, no objective biological markers exist to evaluate most neurodevelopmental disorders. Here, we discuss how systems biology and "omic" approaches can address the mechanistic and biomarker limitations in these afflictions. We present heuristic principles for testing the potential of systems biology to identify mechanisms and biomarkers of disease in the example of Rett syndrome, a neurodevelopmental disorder caused by a well-defined monogenic defect in methyl-CpG-binding protein 2 (MECP2). We propose that such an approach can not only aid in monitoring clinical disease severity but also provide a measure of target engagement in clinical trials. By deepening our understanding of the "big picture" of systems biology, this approach could even help generate hypotheses for drug development programs, hopefully resulting in new treatments for these devastating conditions.

Biliary Tract Disease in Girls and Young Women With Rett Syndrome

OBJECTIVE

We reviewed medical records and conducted a nationwide survey to characterize the clinical features and determine the prevalence of biliary tract disease in girls and women with Rett syndrome (RTT).

METHODS

Sixty-two individuals with RTT and biliary tract disease were identified from the membership of Rett Syndrome Organization and patient files of the principal investigator. Medical records of 46 individuals were reviewed for presenting features, diagnostic tests, and treatment outcomes of biliary tract disease. We designed a questionnaire that probed the frequency of risk factors and treatment outcomes of biliary tract disease in RTT. The questionnaire was completed by 271 parents whose daughters met the clinical criteria for RTT and/or had MECP2 mutations and participated in the Natural History of Rett Syndrome Study.

RESULTS

Presenting symptoms identified by record review included abdominal pain (94%), irritability (88%), weight loss (64%), and vomiting (52%). Biliary dyskinesia, cholecystitis, and cholelithiasis were identified in 90%, 77%, and 70%, respectively, by cholescintigraphy, surgical pathology, and abdominal ultrasound. The prevalence of biliary tract disease was 4.4% (n = 12) in the RTT cohort. Risk factors included older age (P < 0.001) and a positive family history (P < 0.01). Diagnoses included cholecystitis (n = 5), biliary dyskinesia (n = 6), and cholelithiasis (n = 7). Ten individuals underwent surgery; 7 had resolution of symptoms after surgical intervention.

CONCLUSIONS

Biliary tract disease is not unique to RTT, but may be under-recognized because of the cognitive impairment of affected individuals. Early diagnostic evaluation and intervention may improve the health and quality of life of individuals affected with RTT and biliary tract disease.

Rett syndrome before regression: A time window of overlooked opportunities for diagnosis and intervention

Rett syndrome (RTT) is a rare neurological disorder primarily affecting females, causing severe cognitive, social, motor and physiological impairments for which no cure currently exists. RTT clinical diagnosis is based on the peculiar progression of the disease, since patients show an apparently normal initial development with a subsequent sudden regression at around 2 years of age. Accumulating evidences are rising doubts regarding the absence of early impairments, hence questioning the concept of regression. We reviewed the published literature addressing the pre-symptomatic stage of the disease in both patients and animal models with a particular focus on behavioral, physiological and brain abnormalities. The emerging picture delineates subtle, but reliable impairments that precede the onset of overt symptoms whose bases are likely set up already during embryogenesis. Some of the outlined alterations appear transient, suggesting compensatory mechanisms to occur in the course of development. There is urgent need for more systematic developmental analyses able to detect early pathological markers to be used as diagnostic tools and precocious targets of time-specific interventions.

Hand stereotypies: Lessons from the Rett Syndrome Natural History Study

OBJECTIVE

To characterize hand stereotypies (HS) in a large cohort of participants with Rett syndrome (RTT).

METHODS

Data from 1,123 girls and women enrolled in the RTT Natural History Study were gathered. Standard tests for continuous and categorical variables were used at baseline. For longitudinal data, we used repeated-measures linear and logistic regression models and nonparametric tests.

RESULTS

HS were reported in 922 participants with classic RTT (100%), 73 with atypical severe RTT (97.3%), 74 with atypical mild RTT (96.1%), and 17 females with MECP2 mutations without RTT (34.7%). Individuals with RTT who had classic presentation or severe MECP2 mutations had higher frequency and earlier onset of HS. Heterogeneity of HS types was confirmed, but variety decreased over time. At baseline, almost half of the participants with RTT had hand mouthing, which like clapping/tapping, decreased over time. These 2 HS types were more frequently reported than wringing/washing. Increased HS severity (prevalence and frequency) was associated with worsened measures of hand function. Number and type of HS were not related to hand function. Overall clinical severity was worse with decreased hand function but only weakly related to any HS characteristic. While hand function decreased over time, prevalence and frequency of HS remained relatively unchanged and high.

CONCLUSIONS

Nearly all individuals with RTT have severe and multiple types of HS, with mouthing and clapping/tapping decreasing over time. Interaction between HS frequency and hand function is complex. Understanding the natural history of HS in RTT could assist in clinical care and evaluation of new interventions.

Changing conceptualizations of regression: What prospective studies reveal about the onset of autism spectrum disorder

Until the last decade, studies of the timing of early symptom emergence in autism spectrum disorder (ASD) relied upon retrospective methods. Recent investigations, however, are raising significant questions about the accuracy and validity of such data. Questions about when and how behavioral signs of autism emerge may be better answered through prospective studies, in which infants are enrolled near birth and followed longitudinally until the age at which ASD can be confidently diagnosed or ruled out. This review summarizes the results of recent studies that utilized prospective methods to study infants at high risk of developing ASD due to family history. Collectively, prospective studies demonstrate that the onset of ASD involves declines in the rates of key social and communication behaviors during the first years of life for most children. This corpus of literature suggests that regressive onset patterns occur much more frequently than previously recognized and may be the rule rather than the exception.

The importance of anthropological methods in the diagnosis of rare diseases

Most of inborn errors of metabolism (IEMs) and rare endocrine-metabolic diseases (REMD) are rare diseases. According to the European Commission on Public Health, a rare disease is defined, based on its prevalence, as one affecting one in 2000 people. Many IEMs affect body stature, cause craniofacial abnormalities, and disturb the developmental process. Therefore, body proportion, dysmorphic characteristics, and morphological parameters must be assessed and closely monitored. This can be achieved only with the help of an anthropologist who has adequate tools. This is why the role of an anthropologist in collaboration with the physician in the diagnostic process is not to be underestimated. Clinical anthropologists contribute to assessing physical development and improve our understanding of the natural history of rare metabolic diseases. This paper presents anthropometric techniques and methods, such as analysis of demographic data, anthropometric parameters at birth, percentile charts, growth patterns, bioimpedance, somatometric profiles, craniofacial profiles, body proportion indices, and mathematical models of growth curves used in certain rare diseases. Contemporary anthropological methods play an important role in the diagnostic process of rare genetic diseases.

The array of clinical phenotypes of males with mutations in Methyl-CpG binding protein 2

Mutations in the X-linked gene MECP2 are associated with a severe neurodevelopmental disorder, Rett syndrome (RTT), primarily in girls. It had been suspected that mutations in Methyl-CpG-binding protein 2 (MECP2) led to embryonic lethality in males, however such males have been reported. To enhance understanding of the phenotypic spectrum present in these individuals, we identified 30 males with MECP2 mutations in the RTT Natural History Study databases. A wide phenotypic spectrum was observed, ranging from severe neonatal encephalopathy to cognitive impairment. Two males with a somatic mutation in MECP2 had classic RTT. Of the remaining 28 subjects, 16 had RTT-causing MECP2 mutations, 9 with mutations that are not seen in females with RTT but are likely pathogenic, and 3 with uncertain variants. Two subjects with RTT-causing mutations were previously diagnosed as having atypical RTT; however, careful review of the clinical history determined that an additional 12/28 subjects met criteria for atypical RTT, but with more severe clinical presentation and course, and less distinctive RTT features, than females with RTT, leading to the designation of a new diagnostic entity, male RTT encephalopathy. Increased awareness of the clinical spectrum and widespread comprehensive genomic testing in boys with neurodevelopmental problems will lead to improved identification.