Daniel C. Tarquinio

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

Background Rett syndrome (RTT), a neurodevelopmental disorder that primarily affects girls, is characterised by a period of apparently normal development until 6–18 months of age when motor and communication abilities regress. More than 95% of individuals with RTT have mutations in methyl-CpG-binding protein 2 (MECP2), whose protein product modulates gene transcription. Surprisingly, although the disorder is caused by mutations in a single gene, disease severity in affected individuals can be quite variable. To explore the source of this phenotypic variability, we propose that specific MECP2 mutations lead to different degrees of disease severity. Methods Using a database of 1052 participants assessed over 4940 unique visits, the largest cohort of both typical and atypical RTT patients studied to date, we examined the relationship between MECP2 mutation status and various phenotypic measures over time. Results In general agreement with previous studies, we found that particular mutations, such as p.Arg133Cys, p.Arg294X, p.Arg306Cys, 3° truncations and other point mutations, were relatively less severe in both typical and atypical RTT. In contrast, p.Arg106Trp, p.Arg168X, p.Arg255X, p.Arg270X, splice sites, deletions, insertions and deletions were significantly more severe. We also demonstrated that, for most mutation types, clinical severity increases with age. Furthermore, of the clinical features of RTT, ambulation, hand use and age at onset of stereotypies are strongly linked to overall disease severity. Conclusions We have confirmed that MECP2 mutation type is a strong predictor of disease severity. These data also indicate that clinical severity continues to become progressively worse regardless of initial severity. These findings will allow clinicians and families to anticipate and prepare better for the needs of individuals with RTT.

Growth failure and outcome in Rett syndrome: Specific growth references

Objectives: Prominent growth failure typifies Rett syndrome (RTT). Our aims were to 1) develop RTT growth charts for clinical and research settings, 2) compare growth in children with RTT with that of unaffected children, and 3) compare growth patterns among RTT genotypes and phenotypes. Methods: A cohort of the RTT Rare Diseases Clinical Research Network observational study participants was recruited, and cross-sectional and longitudinal growth data and comprehensive clinical information were collected. A reliability study confirmed interobserver consistency. Reference curves for height, weight, head circumference, and body mass index (BMI), generated using a semiparametric model with goodness-of-fit tests, were compared with normative values using Students t test adjusted for multiple comparisons. Genotype and phenotype subgroups were compared using analysis of variance and linear regression. Results: Growth charts for classic and atypical RTT were created from 9,749 observations of 816 female participants. Mean growth in classic RTT decreased below that for the normative population at 1 month for head circumference, 6 months for weight, and 17 months for length. Mean BMI was similar in those with RTT and the normative population. Pubertal increases in height and weight were absent in classic RTT. Classic RTT was associated with more growth failure than atypical RTT. In classic RTT, poor growth was associated with worse development, higher disease severity, and certain MECP2 mutations (pre-C-terminal truncation, large deletion, T158M, R168X, R255X, and R270X). Conclusions: RTT-specific growth references will allow effective screening for disease and treatment monitoring. Growth failure occurs less frequently in girls with RTT with better development, less morbidity typically associated with RTT, and late truncation mutations.

Rett Syndrome: Crossing the Threshold to Clinical Translation

Lying at the intersection between neurobiology and epigenetics, Rett syndrome (RTT) has garnered intense interest in recent years, not only from a broad range of academic scientists, but also from the pharmaceutical and biotechnology industries. In addition to the critical need for treatments for this devastating disorder, optimism for developing RTT treatments derives from a unique convergence of factors, including a known monogenic cause, reversibility of symptoms in preclinical models, a strong clinical research infrastructure highlighted by an NIH-funded natural history study and well-established clinics with significant patient populations. Here, we review recent advances in understanding the biology of RTT, particularly promising preclinical findings, lessons from past clinical trials, and critical elements of trial design for rare disorders.

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.

Growth charts for 22q11 deletion syndrome

The purpose of this work was to create growth curves specific to the 22q11.2 deletion syndrome. Growth parameters on 188 patients (86 females, 102 males) followed by a group of three dysmorphologists were collected by retrospective chart review. Growth charts for body mass, length/height, and head circumference were generated using a semi‐parametric model with goodness‐of‐fit tests. The resulting charts show that between 25 and 50% of children with 22q11.2 deletion syndrome fall below the 2nd centile for the normal population for all growth parameters. Establishing norms of growth for 22q11.2 deletion syndrome allows the clinician to identify and investigate those children who deviate substantially from the growth profile of this condition.

Longitudinal course of epilepsy in Rett syndrome and related disorders

Epilepsy is common in Rett syndrome, an X-linked dominant disorder caused by mutations in the MECP2 gene, and in Rett-related disorders, such as MECP2 duplication. However, neither the longitudinal course of epilepsy nor the patterns of seizure onset and remission have been described in Rett syndrome and related conditions. The present study summarizes the findings of the Rett syndrome Natural History study. Participants with clinical Rett syndrome and those with MECP2 mutations without the clinical syndrome were recruited through the Rett Natural History study from 2006 to 2015. Clinical details were collected, and cumulative lifetime prevalence of epilepsy was determined using the Kaplan-Meier estimator. Risk factors for epilepsy were assessed using Cox proportional hazards models. Of 1205 participants enrolled in the study, 922 had classic Rett syndrome, and 778 of these were followed longitudinally for 3939 person-years. The diagnosis of atypical Rett syndrome with a severe clinical phenotype was associated with higher prevalence of epilepsy than those with classic Rett syndrome. While point prevalence of active seizures ranged from 30% to 44%, the estimated cumulative lifetime prevalence of epilepsy using Kaplan-Meier approached 90%. Specific MECP2 mutations were not significantly associated with either seizure prevalence or seizure severity. In contrast, many clinical features were associated with seizure prevalence; frequency of hospitalizations, inability to walk, bradykinesia, scoliosis, gastrostomy feeding, age of seizure onset, and late age of diagnosis were independently associated with higher odds of an individual having epilepsy. Aggressive behaviour was associated with lower odds. Three distinct patterns of seizure prevalence emerged in classic Rett syndrome, including those who did not have seizures throughout the study, those who had frequent relapse and remission, and those who had relentless seizures. Although 248 of those with classic Rett syndrome and a history of seizures were in terminal remission at last contact, only 74 (12% of those with a history of epilepsy) were seizure free and off anti-seizure medication. When studied longitudinally, point prevalence of active seizures is relatively low in Rett syndrome, although lifetime risk of epilepsy is higher than previously reported. While daily seizures are uncommon in Rett syndrome, prolonged remission is less common than in other causes of childhood onset epilepsy. Complete remission off anti-seizure medications is possible, but future efforts should be directed at determining what factors predict when withdrawal of medications in those who are seizure free is propitious.

Pubertal development in rett syndrome deviates from typical females

BACKGROUND Rett syndrome is a unique neurodevelopmental disorder, affecting approximately one in 10,000 live female births, most experiencing reduced growth. We characterized pubertal trajectories in females with Rett syndrome. We hypothesized that pubertal trajectory deviates from the general female population with early pubertal onset and delayed menarche. METHODS Participants were individuals enrolled in the Rett Syndrome Natural History Study with clinical diagnosis of Rett syndrome or mutations in MECP2. Intervals to thelarche, adrenarche, and menarche were assessed by survival analysis; body mass index, mutation type, clinical severity, and pubertal milestone relationships were assessed by log-likelihood test; pathway synchrony (relationship between thelarche, adrenarche, and menarche) was assessed by chi-squared analysis. RESULTS Compared with the general female population, more than 25% initiated puberty early, yet entered menarche later (median age 13.0 years). A total of 19% experienced delayed menarche. Median length of puberty, from thelarche to menarche, was 3.9 years. Higher body mass index correlated with earlier thelarche and adrenarche but not menarche; milder mutations correlated with earlier menarche; and milder clinical presentation correlated with earlier thelarche and menarche. Fifty-two percent entered puberty in synchrony, but different from the general population, 15% led with thelarche and 32% with adrenarche. CONCLUSIONS Pubertal trajectories in Rett syndrome differ from general population, entering puberty early and reaching menarche later. Body mass index affects pubertal timing, but the relationship between specific mutations, clinical presentation, and underlying neuroendocrine pathology is less clear.

A Novel Parent Questionnaire for the Detection of Seizures in Children.

BACKGROUND We developed a seizure questionnaire that could be administered by a trained research assistant in a two-step process, approximating the clinical diagnostic process of a pediatric epileptologist. This questionnaire was designed to study seizure prevalence in a research population of 10-year-old children at risk for epilepsy. METHODS English-speaking parents of children 6 months to 12 years old were recruited from the pediatric neurology clinics at Boston Medical Center and interviewed using a computerized questionnaire. An algorithm of parent responses rendered a 4-level ranking scale of seizure probability for events: (1) not likely, (2) indeterminate, (3) probable, (4) almost certain. Blinded to questionnaire results, pediatric neurologists served as the diagnostic gold standard, ranking each patient event using the same four-level scale based on clinical history and examination. RESULTS The questionnaire was completed by 150 of 177 (84.7%) enrolled parents. Seizure prevalence among participants was 38.6%. The seizure questionnaire yielded a fitted receiver operating characteristic area of 0.93 (95% confidence interval [CI], 0.89-0.97). Based on optimal sensitivity and false-positive fraction, we dichotomized the questionnaire results as consistent with seizure (levels 3 and 4) or without seizure (levels 1 and 2). Overall, findings included a 91.4% sensitivity (95% CI, 84.2%-98.6%) and an 82.6% specificity (95% CI, 74.9%-90.4%). The positive predictive value was 76.8% (95% CI, 66.9%-86.8%) and the negative predictive value was 93.8% (95% CI, 88.6%-99.1%). CONCLUSIONS This pediatric seizure questionnaire was both sensitive and specific for detecting clinically confirmed seizures. This tool may be useful to researchers and clinicians in screening large populations of children, decreasing the time and cost of added neurological assessments.

Placebo-controlled crossover assessment of mecasermin for the treatment of Rett syndrome

To measure the efficacy of mecasermin (recombinant human insulin‐like growth factor 1, rhIGF‐1), for treating symptoms of Rett syndrome (RTT) in a pediatric population using a double‐blind crossover study design.

Early Life Epilepsies are a Comorbidity of Developmental Brain Disorders

Early-life epilepsies are a series of disorders frequently accompanied by a broad range of morbidities that include cognitive, behavioral, neuromuscular, and sleep disturbances; enteric and other forms of autonomic dysfunction; sensory processing difficulties; and other issues. Usually these morbidities cluster together in a single patient. Rather than these being separate conditions, all, including the seizures, are manifestations or coexpressions of developmental brain disorders. Instead of viewing epilepsy as the disease and the other features as comorbidities, approaching early-life epilepsies as part of the spectrum of developmental brain disorders could have implications for multidisciplinary care models, anticipatory guidance, and counseling of parents, as well as the design of randomized trials and targeting important outcomes. Ultimately, such an approach could improve understanding and help optimize outcomes in these difficult to treat disorders of early childhood.