DXA measurements in Rett syndrome reveal small bones with low bone mass

Bone health and bisphosphonate treatment in females with Rett syndrome in a national center

BACKGROUND

Impaired bone health is a common morbidity in Rett syndrome (RTT). We aimed to assess lumbar bone mineral density (BMD) and trabecular bone score (TBS) in females with RTT, and to evaluate the effectiveness of bisphosphonate treatment.

METHODS

This retrospective study included 40 females with RTT, aged 5-22 years, who underwent dual-energy X-ray absorptiometry (DXA) scans during 2019-2024 at a national center for RTT. Data collected included medical treatment, anthropometric measurements, and functional scores.

RESULTS

The median age at the first DXA scan was 10.8 years. The mean L1-4 BMD Z-score was -2.1 ± 1.4, and the mean TBS Z-score was -0.4 ± 1.3. The L1-4 BMD Z-score correlated with height (r = 0.407, p = 0.009), weight (r = 0.551, p < 0.001), BMI (r = 0.644, p < 0.001), and TBS Z-scores (r = 0.594, p = 0.009). Poor L1-4 BMD Z-scores were associated with poor mobility scores (p = 0.05) and valproate treatment (p = 0.016). Nine patients (23%) received zoledronate, for a mean 2 years. The mean age at zoledronate initiation was 9.7 ± 2.3 years. Four completed two DXA scans (pre- and post-treatment); the mean BMD Z-score improved from -2.2 ± 0.9 to -1.4 ± 0.9 after treatment.

CONCLUSIONS

Females with RTT have reduced lumbar BMD, which was associated with anthropometric factors, TBS, mobility, and valproate use. Zoledronate may be effective for some patients.

IMPACT

In a retrospective study of 40 females with Rett syndrome (RTT), low bone mineral density (BMD) correlated with lower anthropometric measurements, impaired mobility, and valproic acid use. The association between BMD and trabecular bone score (TBS) in the context of RTT is a novel finding. Our preliminary data support the effectiveness and safety of zoledronate for treating osteoporosis in patients with RTT. Our findings are important in light of the increasing life expectancy of individuals with RTT, and the consequent need to prioritize bone health in this population.

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.

Bone Fracture in Rett Syndrome: Mechanisms and Prevention Strategies

The present study aimed to evaluate the burden and management of fragility fractures in subjects with Rett syndrome. We searched all relevant medical literature from 1 January 1986 to 30 June 2023 for studies under the search term "Rett syndrome and fracture". The fracture frequency ranges from a minimum of 13.9% to a maximum of 36.1%. The majority of such fractures occur in lower limb bones and are associated with low bone mineral density. Anticonvulsant use, joint contractures, immobilization, low physical activity, poor nutrition, the genotype, and lower calcium and vitamin D intakes all significantly impair skeletal maturation and bone mass accrual in Rett syndrome patients, making them more susceptible to fragility fractures. This review summarizes the knowledge on risk factors for fragility fracture in patients with Rett syndrome and suggests a possible diagnostic and therapeutic care pathway for improving low bone mineral density and reducing the risk of fragility fractures. The optimization of physical activity, along with adequate nutrition and the intake of calcium and vitamin D supplements, should be recommended. In addition, subjects with Rett syndrome and a history of fracture should consider using bisphosphonates.

Decline in gross motor skills in adult Rett syndrome; results from a Danish longitudinal study

Longevity of individuals with neurodevelopmental diseases as Rett syndrome (RTT) has increased and many reach adulthood and old age. There is therefore a need to increase knowledge about the course of RTT in adults in order to improve medical care management and quality of life. We did a longitudinal study to address if a possible decline in motor skills in adults with RTT can be explained by the presence of common medical conditions as epilepsy, breathing disturbance, and scoliosis. Data from the Danish RTT database, medical files, and videos from visits at the national Center for Rett syndrome were reviewed. The study included 24 individuals aged 30-66 years at last visit after a follow-up period of 6-12 years. Results showed a clinically observable and significant decline in gross motor skills using the Rett syndrome Gross Motor Scale (RSGMS) with a tendency of less decline in the individuals with the best motor abilities. The frequencies of comorbidities were high. Decline in RSGMS score was associated with the presence of epilepsy and severe scoliosis that had been conservatively managed. The results emphasize that epilepsy plays a significant role in the adult RTT life and management of severe scoliosis in the younger years has impact on the motor abilities in adulthood.

A Comparison of Lumbar Spine and Lateral Distal Femur Bone Density in Girls With Rett Syndrome

Patients with Rett syndrome (RS) are at risk for low bone mineral density (BMD) and femoral fractures. In patients with RS, assessment with lateral distal femur (LDF) dual-energy X-ray absorptiometry (DXA) is recommended and clinically relevant. This study is the first to assess LDF BMD in girls with RS, and to compare LDF BMD results with lumbar spine BMD results in RS. Method Eleven girls (mean age 8.4 yr) with molecularly diagnosed RS and clinical DXA scan(s) were identified; medical charts were retrospectively reviewed. Baseline and serial lumbar spine and LDF BMD Z-scores were evaluated based on patients' ambulation status, presence of epilepsy, and mutation type. Results At the time of first scan, 8 of 11 patients had normal lumbar spine BMD and low LDF BMD Z-scores. Two patients had fracture history. Fully ambulatory (3) patients had higher lumbar spine and LDF BMD than partially (5) and nonambulatory (3) patients. Patients with epilepsy had lower average BMD at all sites. No difference was seen in lumbar spine or LDF BMD in patients with high-risk BMD mutations. Seven patients had serial DXA scans with an average observation of 5.1 yr (range 3.1 yr to 6.2 yr). Lumbar spine BMD over time was variable, while LDF bone mass accrual occurred at a lower rate than typically developing girls. Conclusion Females with RS exhibited lower BMD Z-scores at the LDF than at the lumbar spine. LDF and lumbar spine results were discordant. Ambulatory status and the presence of epilepsy were related to BMD. LDF BMD accrual deviated from normal as patients aged.

Altered Bone Status in Rett Syndrome

Rett syndrome (RTT) is a monogenic neurodevelopmental disorder primarily caused by mutations in X-linked MECP2 gene, encoding for methyl-CpG binding protein 2 (MeCP2), a multifaceted modulator of gene expression and chromatin organization. Based on the type of mutation, RTT patients exhibit a broad spectrum of clinical phenotypes with various degrees of severity. In addition, as a complex multisystem disease, RTT shows several clinical manifestations ranging from neurological to non-neurological symptoms. The most common non-neurological comorbidities include, among others, orthopedic complications, mainly scoliosis but also early osteopenia/osteoporosis and a high frequency of fractures. A characteristic low bone mineral density dependent on a slow rate of bone formation due to dysfunctional osteoblast activity rather than an increase in bone resorption is at the root of these complications. Evidence from human and animal studies supports the idea that MECP2 mutation could be associated with altered epigenetic regulation of bone-related factors and signaling pathways, including SFRP4/WNT/β-catenin axis and RANKL/RANK/OPG system. More research is needed to better understand the role of MeCP2 in bone homeostasis. Indeed, uncovering the molecular mechanisms underlying RTT bone problems could reveal new potential pharmacological targets for the treatment of these complications that adversely affect the quality of life of RTT patients for whom the only therapeutic approaches currently available include bisphosphonates, dietary supplements, and physical activity.

Bone Health in Childhood Chronic Disease

Many children with chronic disease are now surviving into adulthood. As a result, there is a growing interest in optimizing bone health early in the disease course with the dual goals of improving quality of life during childhood and reducing life-long fracture risk. Risk factors for impaired bone health in these children include immobility, nutritional deficiency, exposure to bone toxic therapies, hormonal deficiencies affecting growth and pubertal development, and chronic inflammation. This review focuses on the chronic diseases of childhood most commonly associated with impaired bone health. Recent research findings and clinical practice recommendations, when available, for specific disorders are summarized.

Methyl-CpG-binding protein 2 (MECP2) mutation type is associated with bone disease severity in Rett syndrome

Background

More than 95% of individuals with RTT have mutations in methyl-CpG-binding protein 2 (MECP2), whose protein product modulates gene transcription. The disorder is caused by mutations in a single gene and the disease severity in affected individuals can be quite variable. Specific MECP2 mutations may lead phenotypic variability and different degrees of disease severity. It is known that low bone mass is a frequent and early complication of subjects with Rett syndrome. As a consequence of the low bone mass Rett girls are at an increased risk of fragility fractures. This study aimed to investigate if specific MECP2 mutations may affects the degree of involvement of the bone status in Rett subjects.

Methods

In 232 women with Rett syndrome (mean age 13.8 ± 8.3 yrs) we measured bone mineral density at whole body and at femur (BMD-FN and BMD-TH) by using a DXA machine (Hologic QDR 4500). QUS parameters were assessed at phalanxes by Bone Profiler-IGEA (amplitude dependent speed of sound: AD-SoS and bone transmission time: BTT). Moreover, ambulation capacity (independent or assisted), fracture history and presence of scoliosis were assessed. We divided the subjects with the most common point mutations in two group based on genotype-phenotype severity; in particular, there has been consensus in recognising that the mutations R106T, R168X, R255X, R270X are considered more severe.

Results

As aspect, BMD-WB, BMD-FN and BMD-TH were lower in subjects with Rett syndrome that present the most severe mutations with respect to subjects with Rett syndrome with less severe mutations, but the difference was statistically significant only for BMD-FN and BMD-TH (p < 0.05). Also both AD-SoS and BTT values were lower in subjects that present the most severe mutations with respect to less severe mutations but the difference was not statistically significant. Moreover, subjects with Rett syndrome with more severe mutations present a higher prevalence of scoliosis (p < 0.05) and of inability to walk (p < 0.05).

Conclusion

This study confirms that MECP2 mutation type is a strong predictor of disease severity in subjects with Rett syndrome. In particular, the subjects with more severe mutation present a greater deterioration of bone status, and a higher prevalence of scoliosis and inability to walk.

Bone status in relation to ambulatory performance in girls with Rett syndrome: a 10-year longitudinal study

BACKGROUND

Low bone mass is a frequent and early complication of girls with Rett syndrome. As a consequence of the low bone mass, Rett patients are at an increased risk of fragility fractures. This study aimed to investigate the long-term influences of mobility on bone status in girls with Rett syndrome.

METHODS

In 58 girls with Rett syndrome, biochemical parameters and quantitative ultrasound parameters at phalanges (amplitude-dependent speed of sound: AD-SoS and bone transmission time: BTT) were measured at baseline and after 5 and 10 years. The subjects were divided into two groups: nonambulatory (n = 28) and ambulatory (n = 30).

RESULTS

In nonambulatory Rett subjects, the values of AD-SoS and BTT were significantly lower than in ambulatory Rett subjects at each time point. However, during the 10-year follow-up both ambulatory and nonambulatory Rett patients showed a similar worsening in their bone status.

CONCLUSION

This longitudinal study suggests that both ambulatory and nonambulatory Rett subjects present a progressive deterioration of bone status as assessed by quantitative ultrasound parameters, and the ambulatory impairment and the nutritional status seem to play a key role in the deterioration of bone status.

Lower incidence of fracture after IV bisphosphonates in girls with Rett syndrome and severe bone fragility

BACKGROUND

Classic Rett Syndrome (RS) is a disabling condition mainly caused by MECP2 mutations. Girls with RS are at risk of developing bone fragility and fractures at a young age which results in pain and may seriously impair quality of life.

OBJECTIVE

To retrospectively assess the safety and efficacy of IV bisphosphonates on fracture, bone mineral density (BMD) and bone markers in RS girls with bone fragility.

METHODS

RS girls received either IV pamidronate (n = 19) or IV zoledronate (n = 1) for 2 years.

RESULTS

Of 20 patients studied (age: 12.5 years [6; 39]), 14 were non-ambulatory. The incidence of fracture decreased from 37 fractures in 20 patients, to 1 fracture during or after treatment (follow-up: 3.1 years [1.5; 5]). The spine BMD Z-score improved from -3.2 [-5.6; -0.1] to -2.2 [-3.8; 0.0], p = 0.0006. Most parents reported decreases in chronic pain and 2 patients started to walk. Urinary calcium excretion decreased from 0.7 [0.18; 1.5] to 0.2 [0.03; 0.67] mM/mM of creatinine (p = 0.0001). Pamidronate was well tolerated.

CONCLUSION

RS girls should be screened for impaired bone mineralization and preventive measures should be taken. In girls experiencing fractures, IV bisphosphonates constitute a beneficial adjuvant treatment to diminish the risk of fracture and restore bone density.

Zoledronic acid improves bone histomorphometry in a murine model of Rett syndrome

Rett syndrome (RTT) is a neurodevelopmental disorder predominately affecting young females, caused by deficiency of the global transcriptional protein methyl CpG binding protein 2 (MeCP2). Osteoblasts express MeCP2 and girls with RTT experience early onset osteoporosis, decreased bone mass and an increased fracture risk. There is no defined treatment for osteoporosis associated with RTT. The present study evaluated the effects of zoledronic acid (ZA), a third generation nitrogen-containing bisphosphonate with primarily anti-osteoclastic activity, in a mouse model of MeCP2 deficiency. Mice received weekly injections of 20μg/kg ZA for six weeks. Due to the shortened lifespan of hemizygous male (Mecp2-null) mice, treatment began at 3weeks of age for this group and corresponding wildtype (WT) male mice. Treatment for heterozygous (HET) and WT female mice began at 8weeks of age. Micro-computed tomography (micro-CT) and dynamic analyses of bone turnover were performed. ZA treatment led to significant increases in bone volume fraction, number, connectivity density and apparent density of trabecular bone in all genotypes of mice. In contrast, cortical bone generally was unaffected by ZA injections. Parameters of bone turnover, including mineral apposition rate, labeled bone surface and bone formation rate decreased after treatment with ZA. Mecp2-null mice had reduced labeled bone surface and bone formation rate compared to WT male mice. The results indicate that ZA treatment significantly improved trabecular bone mass in a murine model of RTT with little effect on cortical bone.

Clinical and biological progress over 50 years in Rett syndrome

In the 50 years since Andreas Rett first described the syndrome that came to bear his name, and is now known to be caused by a mutation in the methyl-CpG-binding protein 2 (MECP2) gene, a compelling blend of astute clinical observations and clinical and laboratory research has substantially enhanced our understanding of this rare disorder. Here, we document the contributions of the early pioneers in Rett syndrome (RTT) research, and describe the evolution of knowledge in terms of diagnostic criteria, clinical variation, and the interplay with other Rett-related disorders. We provide a synthesis of what is known about the neurobiology of MeCP2, considering the lessons learned from both cell and animal models, and how they might inform future clinical trials. With a focus on the core criteria, we examine the relationships between genotype and clinical severity. We review current knowledge about the many comorbidities that occur in RTT, and how genotype may modify their presentation. We also acknowledge the important drivers that are accelerating this research programme, including the roles of research infrastructure, international collaboration and advocacy groups. Finally, we highlight the major milestones since 1966, and what they mean for the day-to-day lives of individuals with RTT and their families.

Clinical Guidelines for Management of Bone Health in Rett Syndrome Based on Expert Consensus and Available Evidence

OBJECTIVES

We developed clinical guidelines for the management of bone health in Rett syndrome through evidence review and the consensus of an expert panel of clinicians.

METHODS

An initial guidelines draft was created which included statements based upon literature review and 11 open-ended questions where literature was lacking. The international expert panel reviewed the draft online using a 2-stage Delphi process to reach consensus agreement. Items describe the clinical assessment of bone health, bone mineral density assessment and technique, and pharmacological and non-pharmacological interventions.

RESULTS

Agreement was reached on 39 statements which were formulated from 41 statements and 11 questions. When assessing bone health in Rett syndrome a comprehensive assessment of fracture history, mutation type, prescribed medication, pubertal development, mobility level, dietary intake and biochemical bone markers is recommended. A baseline densitometry assessment should be performed with accommodations made for size, with the frequency of surveillance determined according to individual risk. Lateral spine x-rays are also suggested. Increasing physical activity and initiating calcium and vitamin D supplementation when low are the first approaches to optimizing bone health in Rett syndrome. If individuals with Rett syndrome meet the ISCD criterion for osteoporosis in children, the use of bisphosphonates is recommended.

CONCLUSION

A clinically significant history of fracture in combination with low bone densitometry findings is necessary for a diagnosis of osteoporosis. These evidence and consensus-based guidelines have the potential to improve bone health in those with Rett syndrome, reduce the frequency of fractures, and stimulate further research that aims to ameliorate the impacts of this serious comorbidity.

Teriparatide in the treatment of recurrent fractures in a Rett patient

Rett syndrome is a common X-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. Patients with Rett syndrome have a low bone mineral density and increased risk of fracture. The present case report describes a successful novel therapeutic intervention with teriparatide with one patient with Rett syndrome, after suffering from recurrent low-trauma fractures at intervals of several years. Because of the severity of bone involvement, the decision was made to treat with teriparatide and subsequently with intravenous bisphosphonate. Since the initiation of the treatment, there was an evident improvement at densitometric and QUS parameters. Furthermore, until the present, no new fractures have appeared. This is the first report in which teriparatide was administered to a subjects with Rett syndrome. In conclusion, this report has shown the effectiveness of teriparatide in the management of osteoporotic fractures in one subjects with Rett syndrome. This report provides evidence that increased knowledge of bone pathology and fracture prevention in Rett subjects is important and should be addressed in future studies.

Longitudinal bone mineral content and density in Rett syndrome and their contributing factors

Bone mass and density are low in females with Rett syndrome. This study used Dual energy x-ray absorptiometry to measure annual changes in z-scores for areal bone mineral density (aBMD) and bone mineral content (BMC) in the lumbar spine and total body in an Australian Rett syndrome cohort at baseline and then after three to four years. Bone mineral apparent density (BMAD) was calculated in the lumbar spine. Annual changes in lean tissue mass (LTM) and bone area (BA) were also assessed. The effects of age, genotype, mobility, menstrual status and epilepsy diagnosis on these parameters were also investigated. The baseline sample included 97 individuals who were representative of the total live Australian Rett syndrome population under 30years in 2005 (n=274). Of these 74 had a follow-up scan. Less than a quarter of females were able to walk on their own at follow-up. Bone area and LTM z-scores declined over the time between the baseline and follow-up scans. Mean height-standardised z-scores for the bone outcomes were obtained from multiple regression models. The lumbar spine showed a positive mean annual BMAD z-score change (0.08) and a marginal decrease in aBMD (-0.04). The mean z-score change per annum for those 'who could walk unaided' was more positive for LS BMAD (p=0.040). Total body BMD mean annual z-score change from baseline to follow-up was negative (-0.03). However this change was positive in those who had achieved menses prior to the study (0.03, p=0,040). Total body BMC showed the most negative change (-0.60), representing a decrease in bone mineral content over time. This normalised to a z-score change of 0.21 once adjusted for the reduced lean tissue mass mean z-score change (-0.21) and bone area mean z-score change (-0.14). Overall, the bone mineral content, bone mineral density, bone area and lean tissue mass z-scores for all outcome measures declined, with the TB BMC showing significant decreases. Weight, height and muscle mass appear to have impacts on bone formation and we recommend that nutritional intake should be closely monitored and a physical activity plan developed to optimise bone health. Pubertal progression should also be assessed in conjunction with serial densitometry assessments to track bone mass and density changes over time.

Effects of antiepileptic drugs on bone health and growth potential in children with epilepsy

BACKGROUND

Bone health may be impaired in children with epilepsy.

OBJECTIVES

Our objective was to characterize bone mineral density (BMD) and bone growth in children receiving antiepileptic drugs (AEDs) and to assess the effects of co-morbidity, vitamin D deficiency, and type of drugs used.

DATA SOURCES

Data were sourced from PubMed, Embase, and Web of Science.

ELIGIBILITY CRITERIA

Cross-sectional, cohort, case-control, or randomized controlled trials reporting BMD or parameters of bone growth.

PARTICIPANTS

Children with epilepsy compared with controls.

INTERVENTIONS

AEDS or ketogenic diet.

STUDY APPRAISAL

The studies were evaluated by one author.

SYNTHESIS METHODS

Studies were categorized as reporting reduced BMD or not at any skeletal site as outcome. A logistic regression was performed for age, percent boys, study design, type of AED, co-morbidity or not, and signs of vitamin D deficiency/osteomalacia or not.

RESULTS

Carbamazepine and valproate were analyzed as monotherapy in 11 studies, and for both drugs a limited decrease in BMD seemed present. For oxcarbazepine, levetiracetam, phenytoin, phenobarbital, and topiramate, only one study with monotherapy was found for each drug, none of which reported decreased bone density. Polytherapy with AEDs seemed to be associated with a larger decrease in bone density than was monotherapy. Although few studies were available on bone growth, these did indicate that bone growth may be impaired among users of AEDs. Ketogenic diet may be associated with decreased bone density. The main determinant of normal BMD was absence of vitamin D deficiency/osteomalacia.

LIMITATIONS

The studies differed in skeletal sites studied and most were cross-sectional. No head-to-head comparisons of AEDs were performed. Children treated with polytherapy or ketogenic diet may have more complicated and severe disease than those treated with monotherapy. The underlying cause of epilepsy and vitamin D deficiency may contribute to impaired bone growth and density.

CONCLUSIONS

Reduced bone density, impaired bone growth, and vitamin D deficiency may be seen in children treated with drugs against epilepsy.

IMPLICATIONS

Measures to correct vitamin D deficiency, calcium intake should be taken.

Biomechanical properties of bone in a mouse model of Rett syndrome

Rett syndrome (RTT) is an X-linked genetic disorder and a major cause of intellectual disability in girls. Mutations in the methyl-CpG binding protein 2 (MECP2) gene are the primary cause of the disorder. Despite the dominant neurological phenotypes, MECP2 is expressed ubiquitously throughout the body and a number of peripheral phenotypes such as scoliosis, reduced bone mineral density and skeletal fractures are also common and important clinical features of the disorder. In order to explore whether MeCP2 protein deficiency results in altered structural and functional properties of bone and to test the potential reversibility of any defects, we have conducted a series of histological, imaging and biomechanical tests of bone in a functional knockout mouse model of RTT. Both hemizygous Mecp2(stop/y) male mice in which Mecp2 is silenced in all cells and female Mecp2(stop/+) mice in which Mecp2 is silenced in ~50% of cells as a consequence of random X-chromosome inactivation, revealed significant reductions in cortical bone stiffness, microhardness and tensile modulus. Microstructural analysis also revealed alterations in both cortical and cancellous femoral bone between wild-type and MeCP2-deficient mice. Furthermore, unsilencing of Mecp2 in adult mice cre-mediated stop cassette deletion resulted in a restoration of biomechanical properties (stiffness, microhardness) towards wild-type levels. These results show that MeCP2-deficiency results in overt, but potentially reversible, alterations in the biomechanical integrity of bone and highlights the importance of targeting skeletal phenotypes in considering the development of pharmacological and gene-based therapies.

Evaluation of current pharmacological treatment options in the management of Rett syndrome: from the present to future therapeutic alternatives

Neurodevelopmental disorders are a large family of conditions of genetic or environmental origin that are characterized by deficiencies in cognitive and behavioral functions. The therapeutic management of individuals with these disorders is typically complex and is limited to the treatment of specific symptoms that characterize each disorder. The neurodevelopmental disorder Rett syndrome (RTT) is the leading cause of severe intellectual disability in females. Mutations in the gene encoding the transcriptional regulator methyl-CpG-binding protein 2 (MECP2), located on the X chromosome, have been confirmed in more than 95% of individuals meeting diagnostic criteria for classical RTT. RTT is characterized by an uneventful early infancy followed by stagnation and regression of growth, motor, language, and social skills later in development. This review will discuss the genetics, pathology, and symptoms that distinguish RTT from other neurodevelopmental disorders associated with intellectual disability. Because great progress has been made in the basic and clinical science of RTT, the goal of this review is to provide a thorough assessment of current pharmacotherapeutic options to treat the symptoms associated with this disorder. Furthermore, we will highlight recent discoveries made with novel pharmacological interventions in experimental preclinical phases, and which have reversed pathological phenotypes in mouse and cell culture models of RTT and may result in clinical trials.

A comparative study of dual-X-ray absorptiometry and quantitative ultrasonography for the evaluating bone status in subjects with Rett syndrome

Rett syndrome, an X-linked neurodevelopmental disorder primarily affecting girls, is frequently characterized by a reduced bone mineral density (BMD) with an increased risk of fragility fractures. The aim of the study was to assess bone status by DXA technique and by quantitative ultrasound (QUS) in subjects with Rett syndrome and to evaluate which DXA or QUS parameters better correlate with clinical features. In 156 Rett subjects (mean age 13.6 ± 8.2 years) and in 62 controls, we measured BMD at femoral neck (BMD-FN) and at total femur (BMD-TF). Apparent volumetric bone mineral density (vBMAD) was also calculated. In all subjects, QUS parameters at phalanges by Bone Profiler-IGEA (amplitude-dependent speed of sound: AD-SoS and bone transmission time: BTT) were evaluated. We found that both DXA parameters and QUS parameters were significantly lower in Rett subjects than in controls. All clinical characteristics were positively correlated to BMD-FN, BMD-TF, AD-SoS, and BTT (p < 0.001) but not with vBMAD-FN. All ultrasonographic parameters were significantly correlated to BMD-FN and BMD-TF, whereas vBMAD-FN showed only positive significant correlation with densitometric parameters (p < 001). In Rett subjects BMD-FN was predicted primarily by weight and movement capacity, whereas vBMAD-FN was predicted by weight, height, and calcium intake. Moreover, AD-SoS was predicted by weight, height, and age, while BTT was predicted only by height. In conclusion, in our study the performance of QUS at phalanges was similar to those of BMD at femur, therefore, both areal BMD at femur and QUS at phalanges (AD-SoS and BTT) may be equally useful in the evaluation of skeletal status in Rett patients.

Low bone mineral mass is associated with decreased bone formation and diet in girls with Rett syndrome

OBJECTIVE

The aim of the present study was to characterize biomarkers of bone turnover and their relation with bone mineral mass in a cross-sectional cohort of girls with Rett syndrome (RTT) and to examine the role of dietary, biochemical, hormonal, and inflammatory factors on bone mineral mass and bone biomarkers in this disorder.

METHODS

Total body bone mineral content (BMC) and bone mineral density (BMD) were determined by dual-energy x-ray absorptiometry. Dietary nutrient intakes were determined from 3-day food records. Biomarkers of bone turnover, bone metabolites, vitamin D metabolites, hormones, and inflammatory markers were measured by standard clinical laboratory methods.

RESULTS

Serum osteocalcin, bone alkaline phosphatase, and C-telopeptide showed significant inverse relations with age in the RTT cohort. Mean osteocalcin concentrations were significantly lower and mean bone alkaline phosphatase concentrations were significantly higher for individual age groups in the RTT cohort than mean values for their respective age ranges in the reference population. Significant inverse associations were identified between urinary calcium losses, expressed as calcium:creatinine ratios, and total body BMC and BMD z scores. Dietary protein, calcium, and phosphorus intakes, expressed as a proportion of Dietary Reference Intakes for age and sex, showed significant positive associations with total body BMD z scores.

CONCLUSIONS

The present study suggests decreased bone formation instead of increased bone resorption may explain in part the deficits in bone mineral mass in RTT and that attention to the adequacy of dietary protein, calcium, and phosphorus intakes may offer an opportunity to improve bone health in RTT.

Bone fractures in children with autistic spectrum disorder

BACKGROUND

Bone fractures in children represent a source of significant disability and morbidity. Are children with autistic spectrum disorder (ASD) at an altered risk of fractures compared with typically developing children?

METHODS

Using the General Practice Research Database, the authors assessed the prevalence of fractures in boys with ASD diagnosed between 2 and 8 years. A cross-sectional design was used to compare the prevalence of fractures among children with ASD and age-matched controls, conditional logistic regression to explore the relative risk of having a fracture in association with diagnosed ASD.

RESULTS

The study population comprised 3,219 boys with a first-time diagnosis of ASD and 12,265 matched controls. ASD was associated with a significantly decreased risk of developing a fracture at any time in childhood (odds ratio [OR], 0.68, 95% confidence interval [CI], 0.59-0.77, p < .0001). The relative risk estimates were lower for the time period after ASD diagnosis (OR, 0.56, 95% CI, 0.48-0.66, p < .0001) but were not different for the time period before ASD diagnosis (OR, 0.96, 95% CI, 0.78-1.18, p = .6866). Adjusting for use of different drugs did not change the estimates.

CONCLUSION

The relative risk of experiencing a fracture at any time in childhood is lower for boys with ASD compared with healthy boys.

Low bone turnover phenotype in Rett syndrome: results of biochemical bone marker analysis

BACKGROUND

Patients with Rett syndrome (RTT) are at risk of having low bone mass and low-energy fractures.

METHODS

We characterized bone metabolism by both bone formation and resorption markers in blood in a RTT population of 61 girls and women and 122 well-matched healthy controls. Levels of N-terminal propeptides of collagen type 1 (P1NP), C-terminal telopeptide cross links (CTX), osteocalcin (OC), and bone-specific alkaline phosphatase (B-ALP) were compared between RTT patients and controls in regression models adjusted for BMI, vitamin D status, volumetric bone mineral apparent density of the lumbar spine (vBMAD spine), and femoral neck (vBMAD neck). We examined biochemical bone marker levels overall and stratified to persons younger than age 25 y or equal to or older than age 25 y.

RESULTS

The RTT patients had reduced levels of all biochemical bone markers (P < 0.05), which remained significant in persons younger than 25 y (P ≤ 0.001) regarding P1NP, CTX, and OC. Bone marker levels were not significantly associated to methyl-CpG-binding protein 2 (MECP2) mutation group, walking ability, or previous low-energy fractures.

CONCLUSION

Our findings of a low bone turnover state in girls with RTT suggest critical attention to medical treatment of low bone mass in young RTT patients.

Pubertal trajectory in females with Rett syndrome: a population-based study

BACKGROUND

Rett syndrome is a severe genetic neurodevelopmental disorder mainly affecting females. The aim of this study was to describe pubertal development in a population-based cohort of females with Rett syndrome.

METHODS

To assess pubertal trajectory we used six waves of data provided by parents of girls and women, recruited through the Australian population-based Rett Syndrome Database. The age at which adrenarche, thelarche or menarche occurred was used as the parameter for time to event (survival) analysis. The relationships between BMI, mutation type and the trajectories were investigated, using Cox proportional hazards.

RESULTS

One quarter of girls reached adrenarche by 9.6 years, half by 11 years and three quarters by 12.6 years. Half reached menarche by 14 years (range 8-23). Being underweight was associated with later age at adrenarche, thelarche and menarche, while higher BMI (overweight) was associated with earlier onset. In general, girls with C-terminal deletions and early truncating mutations reached pubertal stages earlier and those with the p.R168X mutation reached them later.

CONCLUSION

The pubertal course in Rett syndrome may be abnormal, sometimes with early adrenarche but delayed menarche. These features may be genotype dependent and may have varying relationships with growth and bone acquisition.

MeCP2 modulates the canonical Wnt pathway activation by targeting SFRP4 in rheumatoid arthritis fibroblast-like synoviocytes in rats

Rheumatoid arthritis (RA) is an autoimmune disease characterized by the rheumatoid factor and anti-citrullinated peptide antibody (ACPA) against common autoantigens that are widely expressed within and outside the joints. Many factors participate in the pathogenesis of RA, such as cytokine imbalance, Wnt pathway activation, matrix production, and osteoprotegerin on osteoclasts. Fibroblast-like synoviocytes (FLS) activation has an important role in RA pathogenesis. The methyl-CpG-binding protein (MeCP2) which promoted repressed chromatin structure was selectively detected in synovium of diseased articular in rats. Overexpression of this protein results in an up-regulation of global methylation levels and transcriptional suppression of specific genes. There were increased MeCP2 and decreased secreted frizzled-related protein 4 (SFRP4) in synovium as well as the FLS isolated from the synovium of RA rats. Knockdown of MeCP2 using siRNA technique enhanced SFRP4 expression in both mRNA and protein levels in FLS. These results indicated that epigenetic modification was involved in differential expression of SFRP4. To further explore the underlying molecular mechanisms, we hypothesized that the SFRP4 down-regulation in synovium was caused by DNA methylation. Treatment of FLS with DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-azadC) blocked the cell proliferation and increased the SFRP4 expression. Increased SFRP4 down-regulated the key gene β-catenin, the downstream effectors gene ccnd1 and fibronectin expression in canonical Wnt pathway at the same time. MeCP2 and DNA methylation may provide molecular mechanisms for canonical Wnt pathway activation in RA. Combination of 5-azadC and MeCP2 may be a promising treatment strategy for individuals with RA in which SFRP4 is inactivated.

Gastrointestinal and nutritional problems occur frequently throughout life in girls and women with Rett syndrome

OBJECTIVE

We conducted a nationwide survey to determine the prevalence of common gastrointestinal and nutritional disorders in Rett syndrome (RTT) based on parental reporting and related the occurrence of these problems to age and methyl-CpG-binding protein 2 (MECP2) gene status.

METHODS

We designed a questionnaire that probed symptoms, diagnoses, diagnostic tests, and treatment interventions related to gastrointestinal and nutritional problems in RTT. The International Rett Syndrome Foundation distributed the questionnaire to 1666 family-based members and forwarded their responses for our review. We interrogated the Rare Disease Clinical Research Network database to supplement findings related to medications used to treat gastrointestinal problems in RTT.

RESULTS

Parents of 983 female patients with RTT (59%) responded and identified symptoms and diagnoses associated with gastrointestinal dysmotility (92%), chewing and swallowing difficulties (81%), weight deficits or excess (47%), growth deficits (45%), low bone mineral content or fractures (37%), and biliary tract disorders (3%). Height-for-age, weight-for-age, and body mass index z scores decreased significantly with age; height- and weight-, but not body mass index-for-age z scores were significantly lower in female subjects with MECP2 mutations than in those without. Vomiting, nighttime awakening, gastroesophageal reflux, chewing difficulty, and choking with feeding were significantly less likely to occur with increasing age. Short stature, low bone mineral content, fractures, and gastrostomy placement were significantly more likely to occur with increasing age. Chewing difficulty, choking with feeding, and nighttime awakening were significantly less likely to occur, whereas short stature was significantly more likely to occur, in female subjects with MECP2 mutations than in those without. Diagnostic evaluations and therapeutic interventions were used less frequently than the occurrence of symptoms or diagnoses in the RTT cohort.

CONCLUSIONS

Gastrointestinal and nutritional problems perceived by parents are prevalent throughout life in girls and women with RTT and may pose a substantial medical burden for their caregivers. Physician awareness of these features of RTT may improve the health and quality of life of individuals affected with this disorder.

The relationship between serum ghrelin and body composition with bone mineral density and QUS parameters in subjects with Rett syndrome

Several studies have reported that females with Rett's syndrome frequently have marked decreases in bone mineral density (BMD). However, the pathogenesis of impaired bone status in RTT girls remains controversial. This study aimed to investigate whether ghrelin, an orexigenic peptide secreted by the stomach, was associated with body composition parameters, bone mineral density and quantitative ultrasound (QUS) in girls with Rett's syndrome. In 123 Rett girls (13.6±8.2 years) and in 55 similar age range controls we evaluated ghrelin serum levels, 25OHD, quantitative ultrasound parameters at phalanxes by Bone Profiler-IGEA (amplitude dependent speed of sound: AD-SoS and bone transmission time: BTT), total body bone mineral density (BMD-WB) by Hologic QDR 4500. Whole body mineral content (BMC-WB), BMC-WB/height, fat mass (FM), fat percentage and lean mass (LM) were determined by using the same DXA device. We found that serum ghrelin levels were significantly higher in the Rett patients with respect to the control group (p<0.05). In Rett girls ghrelin serum levels were inversely correlated with both age (R(2)=0.17, p<0.001) and BMI (R(2)=0.14, p<0.001). Moreover, in Rett subjects the values of BMD-WB, BMC-WB, BMC-WB/height and QUS parameters were significantly lower than in control subjects. Fat mass and lean mass were lower in Rett subjects than in controls, but the difference reached the statistical significance only for lean mass. In Rett girls ghrelin serum levels were not predictors of bone status. Instead, we found that in Rett subjects, lean mass, age and 25OHD were significant independent predictors of BMC-WB/h, whereas both age and height were independent predictors of BMD-WB. Moreover, AD-SoS was predicted by age, fat percentage and height; while BTT was predicted only by height. In conclusion, our findings indicate that ghrelin levels were higher in Rett girls with respect to healthy controls, and negatively associated with both DXA and QUS parameters. However, in our study ghrelin was not found to be an independent predictor of bone mass, so supporting the hypothesis that ghrelin is elevated in Rett subjects in a compensatory manner.