Osteopenia in Rett syndrome

Early Complications After Posterior Spinal Fusion in Patients With Rett Syndrome

BACKGROUND

Neuromuscular scoliosis in Rett syndrome (RS) is common, progressive, and often requires posterior spinal fusion (PSF). While PSF is associated with improved overall outcomes, there is a paucity of information describing complications. We aimed to report the postoperative complications, readmissions, and reoperations for patients with RS undergoing PSF.

METHODS

Female pediatric patients with RS treated by PSF with segmental instrumentation, with or without concurrent pelvis fixation, during January 2012 to August 2022 were included. Preoperative patient characteristics, intraoperative data (estimated blood loss, cell saver, packed red blood cells transfused), postoperative complications according to the Modified Clavien-Dindo-Sink classification within 90 days, unplanned readmissions within 30 days, and unplanned reoperations within 90 days were recorded.

RESULTS

A total of 25 females were included. The mean (SD) age at surgery was 12.9 (1.8) years and the mean follow-up of 38.6 (24.9) months. The mean preoperative major coronal curve was 79 degrees (23 degrees) which decreased to 32 degrees (15 degrees) by the last follow-up ( P <0.001). The median estimated blood loss was 600 mL and length of stay was 7 days. There were 81 total postoperative complications (3.2 complications/patient). Eight (32%) had grade IVa complications (disseminated intravascular coagulopathy, hypotensive shock, respiratory failure, chronic urosepsis). Five (20%) patients experienced seizures, 48% had pulmonary complications, and 56% had gastrointestinal complications. There were 3 readmissions (12%) within 30 days for pneumonia and 2 (8%) reoperations (an incision and drainage and C2-T2 fusion for significant kyphosis) within 90 days. One patient also had their fusion extended to the pelvis 1 year later. There were more nonambulatory patients in the group fused to the pelvis, but otherwise no differences between those fused and unfused to the pelvis.

CONCLUSIONS

This is the largest review of early postoperative complications for patients with RS who underwent PSF. PSF effectively reduced the major coronal curve, but surgeons and families should be aware of a high postoperative seizure and respiratory complication rate, as well as 8% having reoperations within 90 days and 12% being readmitted within 30 days.

LEVEL OF EVIDENCE

Level IV-therapeutic study.

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.

Oral health care and service utilisation in individuals with Rett syndrome: an international cross-sectional study

BACKGROUND

There is a dearth of literature available on the comparative oral health status of those with Rett syndrome (RTT) despite diurnal bruxism being a supportive diagnostic criterion for the disorder. This study was designed to investigate the dental experiences of individuals with RTT in terms of perceived at-home and professional dental care.

METHODS

Using data in the InterRett database, provided by English-speaking families of individuals with a confirmed MECP2 genetic mutation, the study investigated relationships between dental problems, oral care, child factors including bruxism and use of gastrostomy, and socioeconomic indicators. The study also explored relationships between dental presentations and socioeconomic, child, and family-related factors.

RESULTS

Individuals with RTT exhibiting bruxism were more likely to access dental treatment. Those who had full oral feeding had a higher incidence rate of dental treatment than those with full tube feeding. A conservative (under) estimation of the overall dental caries progression rate revealed that this may be similar to that of the normal population.

CONCLUSIONS

Drivers for dental treatment in RTT include bruxism as well as dental caries. Those who have full oral feeding experience more dental treatment than those with full tube feeding. A higher maternal education level may confer a protective effect for oral health outcomes in those with RTT. Nevertheless, families generally tended to value the importance of oral health despite reported difficulties in day-to-day mouth care.

Treating Rett syndrome: from mouse models to human therapies

Rare diseases are very difficult to study mechanistically and to develop therapies for because of the scarcity of patients. Here, the rare neuro-metabolic disorder Rett syndrome (RTT) is discussed as a prototype for precision medicine, demonstrating how mouse models have led to an understanding of the development of symptoms. RTT is caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2). Mecp2-mutant mice are being used in preclinical studies that target the MECP2 gene directly, or its downstream pathways. Importantly, this work may improve the health of RTT patients. Clinical presentation may vary widely among individuals based on their mutation, but also because of the degree of X chromosome inactivation and the presence of modifier genes. Because it is a complex disorder involving many organ systems, it is likely that recovery of RTT patients will involve a combination of treatments. Precision medicine is warranted to provide the best efficacy to individually treat RTT patients.

Anesthetic management of a Rett syndrome patient with apnea and epilepsy: a case report

Rett syndrome, which is a progressive, central nervous system disease that is caused by a gene mutation, is known to present with various symptoms. This case is that of a 15-year-old girl who was diagnosed with Rett syndrome at the age of 2 years. Laryngotracheal isolation under general anesthesia was planned due to recurrent aspiration pneumonia. Since the patient’s nutritional status and control of convulsions were good, this was deemed an appropriate time for the surgery. Following careful preoperative evaluation of her airway, we performed oral endotracheal intubation using a video laryngoscope after rapid induction. Since postoperative pain control was important to prevent apneic attacks and convulsions, we used a multimodal analgesic regimen including carefully titrated fentanyl, acetaminophen, nonsteroidal anti-inflammatory drug, and wound infiltration with a local anesthetic. Postoperatively, the patient returned to the intensive care unit under spontaneous ventilation and followed a good course. Patients with Rett syndrome present several symptoms. Thus, several points must be considered during the preoperative evaluation, anesthetic management, and postoperative care of these patients.

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.

Bone microarchitecture in Rett syndrome and treatment with teriparatide: a case report

We present the case of a 28-year-old female Rett syndrome patient with low bone mass and a recent fracture who was successfully treated with teriparatide. Bone mineral density and microarchitecture substantially improved after treatment. Rett syndrome (RTT), an X-linked progressive neuro-developmental disorder caused by mutations in the methyl-CpG-binding 2 (MECP2) gene, has been consistently associated with low bone mass. Consequently, patients with RTT are at increased risk of skeletal fractures. Teriparatide is a bone-forming agent for the treatment of osteoporosis that has demonstrated its effectiveness in increasing bone strength and reducing the risk of fractures in postmenopausal women, but, recently, its positive action has also been reported in premenopausal women. We present the case of a 28-year-old female RTT patient with low bone mass and a recent fracture who was successfully treated with teriparatide. Both bone mass measured by DXA and microarchitecture assessed by high resolution peripheral computed tomography (HR pQCT) were substantially improved after treatment.

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.

Osteoblast function and bone histomorphometry in a murine model of Rett syndrome

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder due to mutations affecting the neural transcription factor MeCP2. Approximately 50% of affected females have decreased bone mass. We studied osteoblast function using a murine model of RTT. Female heterozygote (HET) and male Mecp2-null mice were compared to wild type (WT) mice. Micro-CT of tibia from 5 week-old Mecp2-null mice showed significant alterations in trabecular bone including reductions in bone volume fraction (-29%), number (-19%), thickness (-9%) and connectivity density (-32%), and increases in trabecular separation (+28%) compared to WT. We also found significant reductions in cortical bone thickness (-18%) and in polar moment of inertia (-45%). In contrast, cortical and trabecular bone from 8 week-old WT and HET female mice were not significantly different. However, mineral apposition rate, mineralizing surface and bone formation rate/bone surface were each decreased in HET and Mecp2-null mice compared to WT mice. Histomorphometric analysis of femurs showed decreased numbers of osteoblasts but similar numbers of osteoclasts compared to WT, altered osteoblast morphology and decreased tissue synthesis of alkaline phosphatase in Mecp2-null and HET mice. Osteoblasts cultured from Mecp2-null mice, which unlike WT osteoblasts did not express MeCP2, had increased growth rates, but reductions in mRNA expression of type I collagen, Runx2 and Osterix compared to WT osteoblasts. These results indicate that MeCP2 deficiency leads to altered bone growth. Osteoblast dysfunction was more marked in Mecp2-null male than in HET female mice, suggesting that expression of MeCP2 plays a critical role in bone development.

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.

Perioperative management and outcome of patients with Rett syndrome undergoing scoliosis surgery: a retrospective review

BACKGROUND

Rett syndrome is a rare genetically inherited neuromuscular disorder exclusively affecting female patients. Progressive scoliosis is one of the main features of the disease and affected individuals are very likely to need spine correction surgery.

METHODS

We undertook a retrospective notes review of patients with Rett syndrome who had undergone spine surgery from 2005 to 2013. Patients were identified through the hospital's electronic records. The aim of the present study was to identify the anesthetic implications encountered and the perioperative adverse events, in an effort to improve perioperative management and reduce complications.

RESULT

We identified twenty-four children who had 29 procedures in total in this period. Frequent chest infections and poorly controlled epilepsy were the main preoperative findings. There were no adverse events during induction and intubation. Common anesthetic/analgesic drugs were used throughout. Postoperatively, gastrointestinal and respiratory tract complications were the most common. Mean intensive care unit stay was 8.1 days and mean time to discharge from hospital was 26.5 days. We had one in-hospital death.

CONCLUSIONS

Our case series demonstrates a high incidence of complications in this subpopulation, mainly postoperative. Extreme postoperative vigilance is required and recovery in a high dependency unit is highly recommended.

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 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.

Osteoporosis in Rett syndrome: a case study presenting a novel management intervention for severe osteoporosis

The present article describes a successful novel therapeutic intervention with Aredia with one child with Rett syndrome, after suffering from six pathological fractures within less than 3 years due to severe osteoporosis. Since the initiation of the treatment (3 years ago), the child has not suffered any fractures. Patients with chronic diseases and those with disabilities or on anticonvulsant medications are at risk for low bone density and possibly for the resultant pathologic fractures that define osteoporosis in children. Individuals with Rett syndrome (RS) have been shown to have low bone mineral density (or osteopenia) at a young age. If osteoporosis occurs in a girl with RS, it can inflict pain and seriously impair the child's mobility and quality of life. The present article describes a case study of a child with RS (showing an average of 1.75 fractures annually for the 4 years preceding the treatment) before and after a treatment with Aredia. Patient received 30 mg/day for 3 days on a once every 3-month cycle. There was a 45 % improvement in bone mass density (BMD) values from pre-post-intervention. The child had no fractures in the 3 years posttreatment. This finding is significant (p < 0.03). The BMD Z-scores of the child showed severe osteoporosis (Z-score of -3.8) at pre-intervention and are elevated to osteopenia levels (Z-score of -1.3) at post-intervention measurements. All measurements suggest that the treatment successfully reversed the osteoporotic process and prevented further fractures. This change caused great relief to the child and her family and an improvement in their quality of life. The findings support the ability (in one case) to reverse the progression of osteoporosis in individuals with Rett syndrome showing severe osteoporosis with multiple fractures.

Aging in Rett syndrome: a longitudinal study

Little is known about the aging process of people with specific syndromes, like Rett syndrome (RTT). Recognition of the clinical and behavioral characteristics of the adult RTT is needed in order to improve future management of the RTT girl and counseling of parents. In association with the Dutch RTT parent association, a 5-year longitudinal study was carried out. The study population consisted of 53 adult women with a clinical diagnosis of RTT. Postal questionnaires were sent, including demographic features, skills, physical and psychiatric morbidity. At the time of the second measurement seven women had died. In 2012, 80% of the questionnaires (37/46) were returned. Mean age of the women was 31.4 years. Molecular confirmation was possible for 83% of the women for whom analyses were carried out. The adult RTT woman has a more or less stable condition. The general disorder profile is that of a slow on-going deterioration of gross motor functioning in contrast to a better preserved cognitive functioning, less autonomic and epileptic features and good general health. This is the first longitudinal cohort study about aging in RTT. Continuing longitudinal studies are needed to gain more insight into the aging process in RTT.

IGF1 as a Potential Treatment for Rett Syndrome: Safety Assessment in Six Rett Patients

Rett syndrome (RTT) is a devastating neurodevelopmental disorder that affects one in ten thousand girls and has no cure. The majority of RTT patients display mutations in the gene that codes for the methyl-CpG-binding protein 2 (MeCP2). Clinical observations and neurobiological analysis of mouse models suggest that defects in the expression of MeCP2 protein compromise the development of the central nervous system, especially synaptic and circuit maturation. Thus, agents that promote brain development and synaptic function, such as insulin-like growth factor 1 (IGF1), are good candidates for ameliorating the symptoms of RTT. IGF1 and its active peptide, (1–3) IGF1, cross the blood brain barrier, and (1–3) IGF1 ameliorates the symptoms of RTT in a mouse model of the disease; therefore they are ideal treatments for neurodevelopmental disorders, including RTT. We performed a pilot study to establish whether there are major risks associated with IGF1 administration in RTT patients. Six young girls with classic RTT received IGF1 subcutaneous injections twice a day for six months, and they were regularly monitored by their primary care physicians and by the unit for RTT in Versilia Hospital (Italy). This study shows that there are no risks associated with IGF1 administration.

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.

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

Low bone mass is reported in growth-retarded patients harboring mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene causing Rett syndrome (RTT). We present the first study addressing both bone mineral density (BMD) and bone size in RTT. Our object was to determine whether patients with RTT do have low BMD when correcting for smaller bones by examination with dual-energy X-ray absorptiometry (DXA). We compared areal BMD (aBMD(spine) and aBMD(total hip) ) and volumetric bone mineral apparent density (vBMAD(spine) and vBMAD(neck) ) in 61 patients and 122 matched healthy controls. Further, spine and hip aBMD and vBMAD of patients were associated with clinical risk factors of low BMD, low-energy fractures, MECP2 mutation groups, and X chromosome inactivation (XCI). Patients with RTT had reduced bone size on the order of 10% and showed lower values of spine and hip aBMD and vBMAD (p < .001) adjusted for age, pubertal status, and body mass index (BMI). aBMD(spine) , vBMAD(spine) , and aBMD(total hip) were associated with low-energy fractures (p < .05). Walking was significantly associated to aBMD(total hip) and vBMAD(neck) adjusted for age and body mass index (BMI). Further, vBMAD(neck) was significantly associated to a diagnosis of epilepsy, antiepileptic treatment, and MECP2 mutation group, but none of the associations with vBMAD(neck) remained clinically significant in a multiple adjusted model including age and BMI. Neither aBMD(spine) , vBMAD(spine) , nor aBMD(total hip) were significantly associated with epilepsy, antiepileptic treatment, MECP2 mutation group, XCI, or vitamin D status. Low bone mass and small bones are evident in RTT, indicating an apparent low-bone-formation phenotype.

Bone mineral content and density in Rett syndrome and their contributing factors

This study used densitometry to investigate the areal bone mineral density (aBMD) and bone mineral content (BMC) in an Australian Rett syndrome cohort and to assess how factors such as genotype, epilepsy, BMI, and mobility affect these parameters. The influence of lean tissue mass (LTM) and bone area (BA) on total body BMC (TBBMC) was also investigated. Participants, recruited from the Australian Rett Syndrome Database (ARSD), had TBBMC and lumbar spine (LS) and femoral neck (FN) aBMD measured using Dual energy x-ray absorptiometry. Mean height standardized Z scores and CIs for the bone outcomes were obtained from multiple regression models. The mean height Z score for the FN aBMD was low at -2.20, while the LS aBMD was -0.72. The TBBMC mean height Z score was -0.62, although once adjusted for BA and LTM, the mean was above zero, suggesting that low BMC can be explained by narrow bones and decreased muscle mass, likely secondary to decreased mobility. Multiple linear regression identified the p.R168× and p.T158M mutations as the strongest predictors of low aBMC and BMD for all bone outcomes. The strong relationship between genotype, BMC, and aBMD is likely underpinned by the strong relationship between LTM, mobility, and bone outcome measures.

Patients with Rett syndrome sustain low-energy fractures

We present the first case-control study addressing both fracture occurrence and fracture mechanisms in Rett syndrome (RTT). Two previous studies have shown increased fracture risk in RTT. This was also our hypothesis regarding the Danish RTT population. Therefore, we investigated risk factors associated with low-energy trauma and the association to methyl-CpG-binding protein 2 (MECP2) mutations. A total of 61 female patients with RTT and 122 healthy controls matched according to age and pubertal/menopause status were examined by questionnaires, bone biochemical markers in blood, and clinical and x-ray evaluations. National register search on fracture diagnoses was done to obtain complete fracture histories. Our results showed that patients with RTT sustained significantly more low-energy fractures from early age compared with controls, even though overall fracture occurrence apparently was not increased. Low-energy fractures were significantly associated with less mobility and lack of ambulation. Associations with MECP2 mutations or epilepsy were not demonstrated, contrary to previous findings. Blood biochemistry indicated a possible need for D vitamin supplementation in RTT. Our study casts light on fracture occurrence in RTT and points to a need for future research in bone development and fracture risk to establish directions for improved prevention and treatment of low-energy fractures in RTT.

Bone mass in Rett syndrome: association with clinical parameters and MECP2 mutations

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. In 49 female RTT children, aged 1.9-17 y, bone mass was assessed and correlated with clinical parameters and mutations involving the MECP2 gene. We also studied five adult females, aged 20-33 y, and one male child, aged 6 y. Lumbar spine bone mineral content (BMC) and bone mineral density (BMD) were correlated with weight, height, BMI, clinical severity, degree of scoliosis, use of anticonvulsants, and ambulatory status. L1-L4 BMD and BMC showed that 48.9% of them had BMD values >2 SD below age-related norms. BMD values were in the osteoporotic range in the five adult females with RTT. Eleven percent of the children and adults with RTT experienced fractures. Low bone mass was correlated with marginal significance to clinical severity and ambulation but not to scoliosis or anticonvulsant use. Lowest bone mass occurred in patients with T158M or R270X mutations but without statistical significance. Studies in a murine model of RTT confirmed low bone mass as an inherent component of this syndrome. MECP2 mutations and clinical parameters impact bone mass in RTT, but an association with a specific mutation was not demonstrable.

Altered bone matrix mineralization in a patient with Rett syndrome

Rett syndrome (RTT) is a common X-linked neurodevelopmental disorder caused by mutations in the coding region of methyl-CpG-binding 2 (MECP2) gene. Patients with RTT have a low bone mineral density and increased risk of fracture. However, very little is known if bone matrix mineralization is altered in RTT. A 17-year-old girl with a classical form of RTT with a heterozygous nonsense mutation in exon 3 in the MECP2-gene was treated in our hospital. Her femoral neck BMD is 43.3% below the 3rd percentile when compared to age and sex-matched controls. She underwent surgery for correction of her scoliosis, which provided a unique opportunity to obtain bone tissue to study bone matrix mineralization (Bone Mineralization Density Distribution-BMDD) using quantitative backscattered electron imaging (qBEI) and histomorphometry. BMDD outcomes were compared to recently published normative reference data for young individuals. qBEI analysis showed a significant shift to lower matrix mineralization despite histomorphometric indices indicate a low bone turnover. There was a reduction in CaMean (-7.92%) and CaPeak (-3.97%), which describe the degree of mineralization. Furthermore the fraction of low mineralized matrix (CaLow: +261.84%) was dramatically increased, which was accompanied with an increase in the heterogeneity of mineralization (CaWidth: +86.34%). Our findings show a significantly altered bone matrix mineralization of a typical patient with RTT. This may partly explain the low bone density seen in these patients. These results also warrant further studies on the molecular role of MECP2 in bone matrix mineralization.

Mecp2 deficiency decreases bone formation and reduces bone volume in a rodent model of Rett syndrome

Rett syndrome (RTT), a neurological disorder characterized by neurological impairment and a high frequency of osteopenia which often manifests early in childhood, most often is caused by inactivating mutations in the X-linked gene encoding a regulator of epigenetic gene expression, methyl CpG binding protein, MeCP2. Clinical data show that, along with neurological defects, females with RTT frequently have marked decreases in bone mineral density (BMD) beyond that expected from disuse atrophy. To investigate the relationship between loss of Mecp2 and reduced BMD, we used a Mecp2 null mouse model, Mecp2 (-/yBIRD), for our histological and biochemical studies. Mecp2 (-/yBIRD) mice have significantly shorter femurs and an overall reduced skeletal size compared to wild-type mice by post-natal day 60 (P60). Histological and histomorphometric studies identified growth plate abnormalities as well as decreased cortical and trabecular bone in P21 and especially in P60 Mecp2 (-/yBIRD) mice. Dynamic histomorphometry revealed decreased mineral apposition rates (MAR) in Mecp2 null femoral trabecular bone as well as in calvarial bone samples. While changes in MAR of cortical bone were not significant, loss of Mecp2 significantly reduced cortical, trabecular and calvarial bone volume compared with age-matched wild-type animals. These differences indicate that Mecp2 deficiency leads to osteoblast dysfunction, which translates into reduced osteoid deposition accounting for the reduced bone volume phenotype. While individual variations were observed in OPG and Rankl concentrations, molar ratios of OPG:Rankl at P21 and P60 were comparable between wild-type and Mecp2 (-/yBIRD) mice and showed a consistent excess of OPG. In tibial sections, TRAP staining demonstrated equivalent osteoclast number per bone surface measurements between wild-type and null animals. Our work with a Mecp2 null mouse model suggests epigenetic regulation of bone in the Mecp2 (-/yBIRD) mice which is associated with decreased osteoblast activity rather than increased osteoclastic bone loss.

Bone mineral density in children, adolescents, and young adults with epilepsy

PURPOSE

The aim of this study was to assess bone mineral density (BMD) in a large population of children, adolescents, and young adults with epilepsy alone or in association with cerebral palsy and/or mental retardation.

METHODS

Ninety-six patients were enrolled in the study. The group comprised 50 males and 46 females, aged between 3 and 25 years (mean age 11 years). The control group consisted of 63 healthy children and adolescents (23 males, 40 females), aged between 3 and 25 years (mean age 12.1 years). Patients underwent a dual-energy x-ray absorptiometry (DEXA) scan of the lumbar spine (L1-L4) and the z scores were calculated for each patient; the t score was considered for patients 18 years of age or older.

RESULTS

Abnormal BMD was found in 56 patients (58.3%), with values documenting osteopenia in 42 (75%) and osteoporosis in 14 (25%). A significant difference emerged between epileptic patients and the control group in BMD, z score, and body mass index (BMI) (p = <0.001). Lack of autonomous gait, severe mental retardation, long duration of antiepileptic treatment, topiramate adjunctive therapy, and less physical activity significantly correlated with abnormal BMD.

DISCUSSION

This study detected abnormal BMD in more than half of a large pediatric population with epilepsy with or without cerebral palsy and/or mental retardation. The clinical significance of these findings has yet to be clarified.

Eating practices, nutritional status and constipation in patients with Rett syndrome

BACKGROUND: Disturbance in chewing, swallowing and digestive motility may predispose to feeding and nutritional abnormalities in patients with Rett syndrome. OBJECTIVE: To evaluate the dietary habits, nutritional status and the prevalence of constipation in patients with classical Rett syndrome. METHODS: Twenty seven female patients between the ages of 2.6 and 21.8 years were studied. The following parameters were evaluated: food register, weight, height and intestinal movement characteristics. Weight and height were compared with the National Center for Health Statistics standards. RESULTS: The inability to ingest solid foods was observed in 80.8% of the patients. A height-to-age deficit was observed in 13 (48.1%) of the girls, being more intense in patients at stage IV. Weight-for-height deficit was found in 10 (37.0%) patients, 15 (55.6%) showed normal weight and 2 (7.4%) were overweight for their height. The median ingestion of energy, according to weight-for-height, was equal to 106.6%. Insufficient iron ingestion was observed in 63.0% and insufficient calcium in 55.6% of the patients. Constipation was verified in 74.1% of the patients and did not show a relationship with the quantity of fiber in the diet. CONCLUSION: Various nutritional problems, as well as, intestinal constipation were observed in these patients with Rett syndrome, and they must be considered in the multidisciplinary therapeutic planning of these individuals.

Bone mineral content and bone mineral density are lower in older than in younger females with Rett syndrome

Although bone mineral deficits have been identified in Rett syndrome (RTT), the prevalence of low bone mineral density (BMD) and its association with skeletal fractures and scoliosis has not been characterized fully in girls and women with RTT. Accordingly, we measured total body bone mineral content (BMC) and BMD using dual energy x-ray absorptiometry in a cross-sectional group of 50 females, aged 2-38 y, with RTT. Methyl-CpG-binding 2 (MECP2) mutations, skeletal fractures, and scoliosis were documented. The prevalence of BMC and BMD z scores < or-2 SD was 59 and 45%, respectively. Although absolute BMC and BMD increased significantly with increasing age, BMC, and BMD z scores were significantly lower in older than in younger females. The prevalence of fractures and scoliosis was 28 and 64%, respectively. Low BMD z scores were positively associated with fractures and scoliosis. Deficits in BMD were identified across a broad range of MECP2 mutations. This study identified associations among low BMD, fractures, and scoliosis, and underscored the need for better understanding of the molecular mechanisms of MECP2 in the regulation of bone mineral metabolism.

Spinal cord monitoring for scoliosis surgery in Rett syndrome: can these patients be accurately monitored?

STUDY DESIGN

A level III retrospective comparative study.

OBJECTIVE

Assess the clinical efficacy of somatosensory-evoked potential (SSEP) spinal cord monitoring (SCM) in Rett syndrome patients undergoing scoliosis surgery.

SUMMARY OF BACKGROUND DATA

The role of SCM in neuromuscular scoliosis is less accurate compared with idiopathic scoliosis because of the nature of the neuropathic or myopathic disorder. Currently, there are no studies that have specifically addressed the accuracy of SCM in Rett syndrome.

METHODS

A retrospective study to assess the clinical efficacy of SSEP SCM in Rett syndrome patients undergoing scoliosis surgery. Somatosensory-evoked potentials were monitored in 7 patients (8 procedures) with Rett syndrome undergoing scoliosis surgery. Transcranial motor-evoked potentials were not performed because of a concomitant history of seizures. The specific methods of anesthesia and SSEP monitoring were standardized for all patients.

RESULTS

Adequate baseline and intraoperative SSEP measurements could be obtained in all patients. There were no false-negative or false-positive results. There were 7 true-negative and 1 true-positive results during surgery. The latter was a signal amplitude decrease that did not immediately resolve with standard interventions. Consequently, a Stagnara wake-up test was performed that showed spontaneous muscle activity in both lower extremities. No intravenous steroids were given, and the procedure was completed. The patient had transient unilateral lower extremity motor weakness postoperatively, but recovered preoperative muscle function within 24 hours.

CONCLUSIONS

Patients with Rett syndrome undergoing scoliosis surgery can be successfully monitored with SSEPs. A history of seizures is a relative contraindication to transcranial motor-evoked potentials. Monitoring can accurately alert the surgeon to potential intraoperative spinal cord compromise and, therefore, decrease postoperative morbidity.

Bone ultrasonography at phalanxes in patients with Rett syndrome: a 3-year longitudinal study

Osteopenia is a frequent and early complication of Rett syndrome. This study aimed to evaluate the usefulness of Quantitative Ultrasonography (QUS) at phalanxes in the assessment and monitoring of bone status in Rett patients. We studied 109 girls (10.1+/-6.1 years; range 3-25 years) and 101 age-matched controls. Serum calcium (Ca), bone alkaline phosphatase (B-ALP), parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD) and QUS parameters at phalanxes by Bone Profiler-IGEA (amplitude dependent speed of sound: AD-SoS and bone transmission time: BTT) were measured. At baseline both QUS parameters and 25OHD levels were significantly lower in Rett patients than in controls. Serum 25OHD was inversely correlated with serum PTH and BTT Z-score and BTT Z-score was significantly lower (p<0.05) in the girls with a 25OHD serum levels<or=9 ng/ml. Moreover, multiple regression analysis showed that BTT was significantly influenced by 25OHD levels. The design of the study was to carry out a twelve monthly evaluation of QUS and biochemical parameters for 3-years. 82 Rett patients completed the 36 month longitudinal study. During the study period in the patients, who at baseline were non ambulatory, BTT and AD-SoS Z-score presented the tendency to markedly decrease; in contrast, mild changes of the QUS parameters were observed in patients with severe or mild-moderate ambulatory impairment. Significant difference of BTT Z-score and AD-SoS Z-score among the 3 groups of patients categorized on the basis of ambulatory performance were observed at years 2 and 3. The AD-SoS Z-score at the end of the study period were significantly influenced by the changes in ambulatory performance and the use of anticonvulsant therapy. In conclusion our results suggest the usefulness of QUS parameters at phalanxes in the monitoring of bone status in Rett patients. Low levels of 25OHD and ambulatory impairment play a key role in the skeletal deterioration in Rett girls.

Early determinants of fractures in Rett syndrome

OBJECTIVES

The goals were to compare the fracture incidence in Rett syndrome with that in the general population and to investigate the impact of genotype, epilepsy, and early motor skills on subsequent fracture incidence in girls and young women with Rett syndrome.

METHODS

The Australian Rett syndrome study, a population-based study operating since 1993, investigated Australian subjects with Rett syndrome born since 1976. The 234 (81.2%) of 288 verified cases in the Australian Rett syndrome database in 2004 whose families had completed follow-up questionnaires and provided information about fracture history were included in the analyses. The main outcomes were fracture incidence in the Rett syndrome population and fracture risk according to genotype, presence of epilepsy, and early motor profile.

RESULTS

Fracture incidence in this cohort was 43.3 episodes per 1000 person-years, nearly 4 times greater than the population rate. Risk was increased specifically in cases with p.R270X mutations and in cases with p.R168X mutations. Having epilepsy also increased fracture risk, even after adjustment for genotype.

CONCLUSIONS

Girls and young women with Rett syndrome are at increased risk of fracture. Those with mutations found previously to be more severe and those with epilepsy have an increased propensity toward fractures. Improved understanding of the risk factors for fracture could contribute to better targeting of interventions to decrease fracture incidence in this vulnerable population.

Bone mineral density in angelman syndrome

Our aim was to evaluate bone mineral densitometry in patients with Angelman syndrome with or without antiepileptic therapy. Eighteen patients (9 females, 9 males), aged 4.0-24.3 years (mean age, 10.1 years), and two control groups consisting of 18 epileptic and 24 healthy patients, underwent dual-energy X-ray absorptiometry at the lumbar spine (L(1)-L(4)), and z score was evaluated for each patient; the t score was considered for patients aged > or = 18 years. Abnormal bone mineral density was present in 8/18 (44.5%) of patients with Angelman syndrome, in 7/18 (38.9%) of the epileptic group, and in none of the healthy controls. Furthermore, a significant difference regarding mean age of patients (6 versus 15 years, P = 0.008, by Fisher exact test), and mean length of drug treatment (3.5 versus 11.1 years, P = 0.005 by Fisher exact test), appeared in the group with Angelman syndrome. Most of these patients (94.4%) were receiving antiepileptic drugs, mainly valproic acid, for many years. In conclusion, our study revealed osteopenia in almost half the children and young patients with Angelman syndrome. Dual-energy X-ray absorptiometry should be performed in all patients with Angelman syndrome, particularly if they are treated with antiepileptic drugs.

Fractional calcium absorption is increased in girls with Rett syndrome

BACKGROUND

Rett syndrome (RTT), an X-linked neurodevelopmental disorder primarilyaffecting girls, is characterized in part by osteopenia and increased risk of skeletal fractures. We hypothesized that decreased intestinal calcium (Ca) absorption relative to dietary Ca intake and increased renal Ca excretion might cause these problems in RTT.

OBJECTIVE

We measured fractional Ca absorption, urinary Ca loss, dietary Ca intake, and the hormonal factors regulating Ca metabolism to determine whether abnormalities in Ca balance might relate to poor bone mineralization in RTT girls and to evaluate the contribution of these factors to the overall dietary Ca needs of RTT girls.

STUDY DESIGN

Ten RTT girls and 10 controls, matched for age, sex, and pubertal status, were given a 3 day constant Ca diet that mimicked their habitual intakes. At the end of each dietary period, girls received single doses of Ca (intravenous) and Ca (oral). Fractional urinary excretion of Ca, Ca, 24 hour urinary Ca, and urinary cortisol excretion were determined. Serum Ca, phosphorous, alkaline phosphatase, vitamin D metabolites, parathyroid hormone (PTH), and osteocalcin were measured in the postabsorptive state. Bone mineral content (BMC) was measured by dual-energy x-ray absorptiometry.

RESULTS

Fractional Ca absorption was significantly higher in RTT than in control girls (mean +/- SDp, 52 vs. 33 +/- 13%). Dietary Ca intake (mean +/- SDp, 1,100 vs. 1,446 +/- 440 g/d) and net Ca absorption (mean +/- SDp, 513 vs. 362 +/- 306 mg/d) did not differ significantly between RTT and controls, respectively. Although urinary Ca excretion did not differ between groups, the increased urinary Ca:creatinine ratio (mean +/- SDp, 0.39 vs. 0.23 +/- 0.38) was consistent with clinical hypercalcuria and paralleled the significantly increased urinary cortisol excretion (mean +/- SDp, 3.1 vs. 1.7 +/- 1.1 mg/kg lean body mass per day) in the RTT girls. BMC was significantly lower in RTT than in controls (mean +/- SDp, 527 vs. 860 +/- 275 g). Serum Ca, P, alkaline phosphatase, vitamin D metabolites, PTH, and osteocalcin concentrations did not differ between the groups.

CONCLUSION

Fractional Ca absorption showed a compensatory increase in the presence of adequate dietary Ca intakes, mild hypercalcuria, and pronounced bone mineral deficits in RTT girls. Whether supplemental dietary Ca could enhance fractional Ca absorption and improve bone mineralization in RTT girls is unknown.

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Up-regulation of glucocorticoid-regulated genes in a mouse model of Rett syndrome

Rett syndrome (RTT) is a severe form of mental retardation, which is caused by spontaneous mutations in the X-linked gene MECP2. How the loss of MeCP2 function leads to RTT is currently unknown. Mice lacking the Mecp2 gene initially show normal postnatal development but later acquire neurological phenotypes, including heightened anxiety, that resemble RTT. The MECP2 gene encodes a methyl-CpG-binding protein that can act as a transcriptional repressor. Using cDNA microarrays, we found that Mecp2-null animals differentially express several genes that are induced during the stress response by glucocorticoids. Increased levels of mRNAs for serum glucocorticoid-inducible kinase 1 (Sgk) and FK506-binding protein 51 (Fkbp5) were observed before and after onset of neurological symptoms, but plasma glucocorticoid was not significantly elevated in Mecp2-null mice. MeCP2 is bound to the Fkbp5 and Sgk genes in brain and may function as a modulator of glucocorticoid-inducible gene expression. Given the known deleterious effect of glucocorticoid exposure on brain development, our data raise the possibility that disruption of MeCP2-dependent regulation of stress-responsive genes contributes to the symptoms of RTT.

Possible mechanisms of osteopenia in Rett syndrome: bone histomorphometric studies

The etiology of frequently occurring osteoporosis in Rett syndrome is unknown. Five girls, ages 9.75, 11, 12, 13.5, and 14 years, with typical Rett syndrome requiring scoliosis surgery presented an opportunity to study bone remodeling by quantitative bone histomorphometry. Anterior iliac crest bone biopsies taken 1 to 2 days after double labeling of the bone surfaces with tetracycline were submitted for histomorphometry. Bone volume was reduced, and the surface parameters of formation (osteoid surface) were normal, whereas the parameters of resorption (osteoclast surface and number) were decreased. In four girls, the rate of bone formation was reduced but could not be measured in one girl owing to poor labeling. It is possible that the slow rate of bone formation impedes the development and accumulation of peak bone mass and contributes to the decreased bone volume in Rett syndrome. Perhaps MECP2 mutations in Rett syndrome not only influence brain development but also affect bone formation.

Rett syndrome: investigation of nine patients, including PET scan

BACKGROUND

We describe nine females with Rett Syndrome (RS), aged 14 to 26 years. All had had developmental delay before the end of their first year and had subsequently regressed to profound dementia with apraxia, ataxia, irregular respirations and often also seizures.

METHODS

The Revised Gesell developmental assessment and Alpern-Boll Developmental Profile were used in modified form. Volumetric measurements of basal ganglia using MRI were compared with the findings in nine age-matched volunteer females. Positron emission scans with [18F]-6-fluorodopa and [11C]-raclopride were performed under light anesthesia with intravenous Propofol, and the findings were compared with those in healthy control girls. Bidirectional sequencing of the coding regions of the MECP2 gene was investigated in blood samples for mutational analyses.

RESULTS

The RS females functioned at a mental age level ranging from about 4 to 15 months. The scores correlated with height, weight and head circumference. Magnetic resonance scans of basal ganglia showed a significant reduction in the size of the caudate heads and thalami in the Rett cases. Positron emission scans demonstrated that the mean uptake of fluorodopa in RS was reduced by 13.1% in caudate and by 12.5% in putamen as compared to the controls, while dopamine D2 receptor binding was increased significantly by 9.7% in caudate and 9.6% in putamen. Mutations in the coding regions of the MECP2 gene were present in all nine patients. No significant correlation between type and location of mutation and volumetric changes or isotope uptake was demonstrable.

CONCLUSIONS

Our findings suggest a mild presynaptic deficit of nigrostriatal activity in Rett syndrome.

Bone histomorphometry in three females with Rett syndrome

The frequent occurrence of osteoporosis in Rett syndrome raises questions about the etiology of this finding. It is unknown whether there is any relationship between low bone mass and the underlying genetic disorder. We recently had an opportunity to study the status of bone remodeling by quantitative bone histomorphometry in three girls ages 9.75, 13.5, and 14 years, with typical Rett syndrome who required scoliosis surgery.Anterior iliac crest bone biopsies were performed 1-2 days after double labeling of the bone surfaces with tetracycline. Samples were processed for plastic embedding, sectioned, stained, and histomorphometry performed in the cancellous bone. The same observer performed all measurements. Bone volume was reduced, surface parameters of formation (osteoid surface) were normal while parameters of resorption (osteoclast surface and number) were decreased. The rate of bone formation was reduced in the first two girls but could not be measured in the third girl due to lack of double labeling. It may be that the slow rate of bone formation seen in each age group impedes the development and accumulation of peak bone mass and contributes to the decreased bone volume associated with Rett syndrome, although the data is limited. This is the first report to document decreased bone volume determined by quantitative bone histomorphometry in patients with Rett syndrome. With the recent identification of MECP2 mutations in Rett syndrome it is quite likely that genetic factors not only play a major role in brain development but may also influence other organ growth including bone formation.

Z score prediction model for assessment of bone mineral content in pediatric diseases

The objective of this study was to develop an anthropometry-based prediction model for the assessment of bone mineral content (BMC) in children. Dual-energy X-ray absorptiometry (DXA) was used to measure whole-body BMC in a heterogeneous cohort of 982 healthy children, aged 5-18 years, from three ethnic groups (407 European- American [EA], 285 black, and 290 Mexican-American [MA]). The best model was based on log transformations of BMC and height, adjusted for age, gender, and ethnicity. The mean +/- SD for the measured/predicted in ratio was 1.000 +/- 0.017 for the calibration population. The model was verified in a second independent group of 588 healthy children (measured/predicted In ratio = 1.000 +/- 0.018). For clinical use, the ratio values were converted to a standardized Z score scale. The whole-body BMC status of 106 children with various diseases (42 cystic fibrosis [CF], 29 juvenile dermatomyositis [JDM], 15 liver disease [LD], 6 Rett syndrome [RS], and 14 human immunodeficiency virus [HIV]) was evaluated. Thirty-nine patients had Z scores less than -1.5, which suggest low bone mineral mass. Furthermore, 22 of these patients had severe abnormalities as indicated by Z scores less than -2.5. These preliminary findings indicate that the prediction model should prove useful in determining potential bone mineral deficits in individual pediatric patients.

Rett syndrome: review of biological abnormalities

The Rett syndrome (RS) is a peculiar, sporadic, atrophic disorder, almost entirely confined to females. After the first six months of life there is developmental slowing with reduced communication and head growth for about one year. This is followed by a rapid destructive stage with severe dementia and loss of hand skills (with frequent hand wringing), apraxia and ataxia, autistic features and irregular breathing with hyperventilation. Seizures often supervene. Subsequently there is some stabilization in a pseudo-stationary stage during the preschool to school years, associated with more emotional contact but also abnormalities of the autonomic and skeletal systems. After the age of 15-20 years, a late motor deterioration occurs with dystonia and frequent spasticity but seizures become milder. RS has generally been considered an X-linked disorder in which affected females represent a new mutation, with male lethality. Linkage studies suggested a critical region at Xq28. In 1999, mutations in the gene MECP2 encoding X-linked methyl cytosine-binding protein 2 (MeCP2) were found in a proportion of Rett girls. This protein can bind methylated DNA. Analyses are leading to much further investigation of mutants and their effects on genes. Neuropathological and electrophysiological studies of RS are described. Description of neurometabolic factors includes reduced levels of dopamine, serotonin, noradrenaline and choline acetyltransferase (ChAT) in brain, also estimation of nerve growth factors, endorphin, substance P, glutamate and other amino acids and their receptor levels. The results of neuroimaging are surveyed, including volumetric magnetic resonance imaging (MRI) and positron emission tomography (PET).

Molecular approaches to the Rett syndrome gene

Rett syndrome is a neurodevelopmental disorder affecting 1 in 10,000 to 15,000 females worldwide. Apparently normal at birth, girls with Rett syndrome undergo developmental regression and acquire a neurologic and behavioral profile that has been used to define diagnostic criteria for the disorder. Neurochemical and anatomic alterations indicate that Rett syndrome appears to result from an arrest of normal neuronal maturation. Although Rett syndrome generally occurs sporadically, rare familial recurrences indicate a genetic basis for the disorder. Data from familial recurrences are consistent with an X-linked dominant locus causing the classic phenotype in female patients and a distinct, more severe phenotype in hemizygous male patients. Exclusion mapping data from rare kindreds with recurrent Rett syndrome localize the gene to the distal long arm of the X chromosome (Xq27.3-Xqter).

Oropharyngeal dysfunction and gastroesophageal dysmotility are present in girls and women with Rett syndrome

BACKGROUND

Feeding impairment frequently complicates the course of children with neurologic disorders and places them at risk for malnutrition and growth failure. Although feeding abnormalities have been reported in female patients with Rett syndrome, the mechanisms that account for these findings have not been elucidated fully. This study was designed to characterize the clinical features of oropharyngeal and gastroesophageal dysfunction and their impact on the dietary intake and nutritional status of female subjects with Rett syndrome.

METHODS

The clinical features of oropharyngeal and gastroesophageal dysfunction in 13 female patients with Rett syndrome, (age range, 3.7 to 25.7 years) were characterized by an oral feeding assessment, swallowing function study, and upper gastrointestinal series. Growth, nutritional status, and body composition were determined by stadiometry and anthropometry. Dietary intakes were determined from 3-day food records.

RESULTS

Oropharyngeal dysfunction and gastroesophageal dysmotility were present in 100% and 69%, respectively, of the study patients with Rett syndrome. The scope and severity of these abnormalities were apparent only by videofluoroscopy. Abnormalities of oropharyngeal function included poor tongue mobility, reduced oropharyngeal clearance, and laryngeal penetration of liquids and solid food during swallowing. Esophageal dysmotility included absent primary or secondary waves, delayed emptying, atony, the presence of tertiary waves, spasm, and gastroesophageal reflux. Gastric dysmotility included diminished peristalsis or atony. Lower dietary energy intakes were associated with persistence of residue in the valleculae and pyriform sinuses and less body fat.

CONCLUSION

The prevalence of oropharyngeal dysfunction and gastroesophageal dysmotility warrants early diagnostic evaluation and intervention strategies to improve the nutritional status of girls and women with RS.