Elizabeth K. Schorry

Neurofibromatosis in Children: The Role of the Orthopaedist

Type 1 neurofibromatosis (NF-1), also known as von Recklinghausen disease, is one of the most common human single-gene disorders, affecting at least 1 million persons throughout the world. It encompasses a spectrum of multifaceted disorders and may present with a wide range of clinical manifestations, including abnormalities of the skin, nervous tissue, bones, and soft tissues. The condition can be conclusively diagnosed when two of seven criteria established by the National Institutes of Health Consensus Development Conference are met. Most children with NF-1 have no major orthopaedic problems. For those with musculoskeletal involvement, the most important issue is early recognition. Spinal deformity, congenital tibial dysplasia (congenital bowing and pseudarthrosis), and disorders of excessive bone and soft-tissue growth are the three types of musculoskeletal manifestations that require evaluation. Statistics gathered from the Cincinnati Childrens Hospital Neurofibromatosis Center database show the incidence of spinal deformity in children with NF-1 to be 23.6%; pectus deformity, 4.3%; limb-length inequality, 7.1%; congenital tibial dysplasia, 5.7%; hemihypertrophy, 1.4%; and plexiform neurofibromas, 25%. The orthopaedic complications can be managed, but only rarely are they cured.

Social and emotional problems in children with neurofibromatosis type 1: Evidence and proposed interventions

OBJECTIVE To describe social and emotional problems in children and adolescents with neurofibromatosis type 1 (NF1) and propose interventions. Our hypothesis is that children with NF1 will have significantly more social and emotional problems, compared with their unaffected siblings and children in the general population. STUDY DESIGN Forty-three children with NF1 and 22 unaffected siblings (ages 5 to 18 years) were assessed with a standardized test completed by parents and teachers (the Child Behavior Checklist). RESULTS As with other aspects of NF1, there was variable expressivity. However, when rated by parents, children with NF1 had significantly more problems in comparison with test norms or unaffected siblings on 7 of 8 scales: Social Problems, Attention Problems, Anxiety/Depression, Withdrawal, Thought Problems, Somatic Complaints, and Aggressive Behavior. Children with NF1 also scored lower than unaffected siblings on measures assessing sports and other activities. Teachers reported fewer differences. CONCLUSIONS We propose interventions in the form of information for parents; early screening and treatment for speech, motor, and cognitive problems; and an increased level of intervention to prevent and treat psychologic problems, including systematic screening with standardized tests.

Social, emotional, and behavioral functioning of children with NF1

Children with neurofibromatosis type 1 (NF1) can have varying degrees of cognitive impairment, and are at risk for social, emotional, and behavioral dysfunction. We undertook an evaluation of social, emotional, and behavioral functioning of youth with NF1 and peers from multiple perspectives. We hypothesized that children with NF1 would have more psychosocial difficulties, which would be positively associated with neurological involvement. We compared 58 children with NF1, ages 7–15, with comparison classroom peers, classmates who were same race/gender and closest date of birth. Peer relationships, emotional well‐being, and behavior were evaluated from multiple perspectives in multiple settings. Results showed that teachers perceived children with NF1 as more prosocial (i.e., polite, helpful to others). Teachers and peers viewed children with NF1 as displaying less leadership behavior and as more socially sensitive‐isolated (i.e., often left out, trouble making friends). Children with NF1 had fewer friendships and were less well liked by peers. Mothers and fathers reported more problems with social functioning among children with NF1. Few group differences in emotional well‐being and behavior were identified according to child and father report. However, mothers perceived children with NF1 to have more emotional problems relative to comparison peers, predominantly among older children. Neurological involvement was significantly related to psychosocial problems. We conclude that children with NF1 are frequently socially isolated and rejected by peers; and that greater neurological involvement is associated with more emotional problems. Central nervous system involvement appears to play a key role in identifying children at risk for problems with friendships, social acceptance, and emotional functioning (i.e., depression).

Blood expression profiles for tuberous sclerosis complex 2, neurofibromatosis type 1, and down's syndrome

Blood gene expression profiling has been applied to a variety of hematological malignancies, autoimmune disorders, and infectious diseases. This study applies this approach to genetic diseases without obvious blood phenotypes. Three genetic diseases including tuberous sclerosis complex 2, neurofibromatosis type 1, and Downs syndrome were compared with a group of healthy controls. RNA from whole blood was surveyed using Affymetrix U133A arrays. Each disease was associated with a unique gene expression pattern in blood that can be accurately distinguished by a classifier. Genes on chromosome 21 were overexpressed in Downs syndrome, and genes controlling cell cycle and proliferation were associated with tuberous sclerosis complex type 2 or neurofibromatosis type 1. A subset of genes involved in cardiac development or remodeling were overexpressed in patients with Downs syndrome and congenital heart defects. These findings suggest that blood gene expression profiling on a broader basis might be useful for genetic disease screening/diagnosis and might help elucidate mechanisms and pathways that lead to genotype–phenotype differences. Ann Neurol 2004

Skeletal abnormalities in neurofibromatosis type 1: Approaches to therapeutic options

The skeleton is frequently affected in individuals with neurofibromatosis type 1, and some of these bone manifestations can result in significant morbidity. The natural history and pathogenesis of the skeletal abnormalities of this disorder are poorly understood and consequently therapeutic options for these manifestations are currently limited. The Childrens Tumor Foundation convened an International Neurofibromatosis Type 1 Bone Abnormalities Consortium to address future directions for clinical trials in skeletal abnormalities associated with this disorder. This report reviews the clinical skeletal manifestations and available preclinical mouse models and summarizes key issues that present barriers to optimal clinical management of skeletal abnormalities in neurofibromatosis type 1. These concepts should help advance optimal clinical management of the skeletal abnormalities in this disease and address major difficulties encountered for the design of clinical trials.

Clinical Impact and Cost-Effectiveness of Whole Exome Sequencing as a Diagnostic Tool: A Pediatric Center’s Experience

Background There are limited reports of the use of whole exome sequencing (WES) as a clinical diagnostic tool. Moreover, there are no reports addressing the cost burden associated with genetic tests performed prior to WES. Objective We demonstrate the performance characteristics of WES in a pediatric setting by describing our patient cohort, calculating the diagnostic yield, and detailing the patients for whom clinical management was altered. Moreover, we examined the potential cost-effectiveness of WES by examining the cost burden of diagnostic workups. Methods To determine the clinical utility of our hospital’s clinical WES, we performed a retrospective review of the first 40 cases. We utilized dual bioinformatics analyses pipelines based on commercially available software and in-house tools. Results Of the first 40 clinical cases, we identified genetic defects in 12 (30%) patients, of which 47% of the mutations were previously unreported in the literature. Among the 12 patients with positive findings, seven have autosomal dominant disease and five have autosomal recessive disease. Ninety percent of the cohort opted to receive secondary findings and of those, secondary medical actionable results were returned in three cases. Among these positive cases, there are a number of novel mutations that are being reported here. The diagnostic workup included a significant number of genetic tests with microarray and single-gene sequencing being the most popular tests. Significantly, genetic diagnosis from WES led to altered patient medical management in positive cases. Conclusion We demonstrate the clinical utility of WES by establishing the clinical diagnostic rate and its impact on medical management in a large pediatric center. The cost-effectiveness of WES was demonstrated by ending the diagnostic odyssey in positive cases. Also, in some cases it may be most cost-effective to directly perform WES. WES provides a unique glimpse into the complexity of genetic disorders.

Activity of Selumetinib in Neurofibromatosis Type 1–Related Plexiform Neurofibromas

BACKGROUND Effective medical therapies are lacking for the treatment of neurofibromatosis type 1-related plexiform neurofibromas, which are characterized by elevated RAS-mitogen-activated protein kinase (MAPK) signaling. METHODS We conducted a phase 1 trial of selumetinib (AZD6244 or ARRY-142886), an oral selective inhibitor of MAPK kinase (MEK) 1 and 2, in children who had neurofibromatosis type 1 and inoperable plexiform neurofibromas to determine the maximum tolerated dose and to evaluate plasma pharmacokinetics. Selumetinib was administered twice daily at a dose of 20 to 30 mg per square meter of body-surface area on a continuous dosing schedule (in 28-day cycles). We also tested selumetinib using a mouse model of neurofibromatosis type 1-related neurofibroma. Response to treatment (i.e., an increase or decrease from baseline in the volume of plexiform neurofibromas) was monitored by using volumetric magnetic resonance imaging analysis to measure the change in size of the plexiform neurofibroma. RESULTS A total of 24 children (median age, 10.9 years; range, 3.0 to 18.5) with a median tumor volume of 1205 ml (range, 29 to 8744) received selumetinib. Patients were able to receive selumetinib on a long-term basis; the median number of cycles was 30 (range, 6 to 56). The maximum tolerated dose was 25 mg per square meter (approximately 60% of the recommended adult dose). The most common toxic effects associated with selumetinib included acneiform rash, gastrointestinal effects, and asymptomatic creatine kinase elevation. The results of pharmacokinetic evaluations of selumetinib among the children in this trial were similar to those published for adults. Treatment with selumetinib resulted in confirmed partial responses (tumor volume decreases from baseline of ≥20%) in 17 of the 24 children (71%) and decreases from baseline in neurofibroma volume in 12 of 18 mice (67%). Disease progression (tumor volume increase from baseline of ≥20%) has not been observed to date. Anecdotal evidence of decreases in tumor-related pain, disfigurement, and functional impairment was observed. CONCLUSIONS Our early-phase data suggested that children with neurofibromatosis type 1 and inoperable plexiform neurofibromas benefited from long-term dose-adjusted treatment with selumetinib without having excess toxic effects. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01362803 .).

Genotype-Phenotype Correlations in Rubinstein-Taybi Syndrome

Rubinstein–Taybi syndrome (RTS) is a rare multiple congenital anomaly/intellectual impairment syndrome. Loss of function in CREBBP or EP300 genes has been found in about 50% of patients with RTS. Genotype–phenotype correlations were investigated in 93 patients meeting diagnostic criteria for RTS during 2 international RTS family conferences. Mutation analysis of CREBBP was performed on all 31 coding exons and exon–intron junctions; a subset of patients had FISH analysis for large deletions. A total of 64 different variations were observed in the DNA sequence, and determined to be definitive mutations in 52 patients (56%). Mutations detected included: 10 missense mutations; 36 truncating or splice‐site mutations; and 6 large deletions detectable by FISH. Fourteen patients had synonymous changes of unknown significance. The majority of mutations affected the HAT domain of CREBBP or predicted termination of the protein before the HAT region. Extensive phenotypic data were collected on each patient and analyzed to determine correlations with mutation types, that is, truncating, large deletions, single amino acid substitutions, or no CREBBP mutation. All four groups displayed the characteristic facial and thumb dysmorphology. Growth retardation in height and weight was seen more frequently in patients with no CREBBP mutation; seizure disorder was more frequent in those with CREBBP mutations. Degree of mental retardation was similar in all groups, although there was a trend toward lower IQ and autistic features in patients with large deletions. Similarity in phenotype between the groups implies that the several genes involved in causing RTS likely have effects through the same pathway.

Mutations in PIEZO2 Cause Gordon Syndrome, Marden-Walker Syndrome, and Distal Arthrogryposis Type 5

Gordon syndrome (GS), or distal arthrogryposis type 3, is a rare, autosomal-dominant disorder characterized by cleft palate and congenital contractures of the hands and feet. Exome sequencing of five GS-affected families identified mutations in piezo-type mechanosensitive ion channel component 2 (PIEZO2) in each family. Sanger sequencing revealed PIEZO2 mutations in five of seven additional families studied (for a total of 10/12 [83%] individuals), and nine families had an identical c.8057G>A (p.Arg2686His) mutation. The phenotype of GS overlaps with distal arthrogryposis type 5 (DA5) and Marden-Walker syndrome (MWS). Using molecular inversion probes for targeted sequencing to screen PIEZO2, we found mutations in 24/29 (82%) DA5-affected families and one of two MWS-affected families. The presence of cleft palate was significantly associated with c.8057G>A (Fishers exact test, adjusted p value < 0.0001). Collectively, although GS, DA5, and MWS have traditionally been considered separate disorders, our findings indicate that they are etiologically related and perhaps represent variable expressivity of the same condition.

Mutations in SLC25A46, encoding a UGO1-like protein, cause an optic atrophy spectrum disorder

Dominant optic atrophy (DOA) and axonal peripheral neuropathy (Charcot-Marie-Tooth type 2, or CMT2) are hereditary neurodegenerative disorders most commonly caused by mutations in the canonical mitochondrial fusion genes OPA1 and MFN2, respectively. In yeast, homologs of OPA1 (Mgm1) and MFN2 (Fzo1) work in concert with Ugo1, for which no human equivalent has been identified thus far. By whole-exome sequencing of patients with optic atrophy and CMT2, we identified four families with recessive mutations in SLC25A46. We demonstrate that SLC25A46, like Ugo1, is a modified carrier protein that has been recruited to the outer mitochondrial membrane and interacts with the inner membrane remodeling protein mitofilin (Fcj1). Loss of function in cultured cells and in zebrafish unexpectedly leads to increased mitochondrial connectivity, while severely affecting the development and maintenance of neurons in the fish. The discovery of SLC25A46 strengthens the genetic overlap between optic atrophy and CMT2 while exemplifying a new class of modified solute transporters linked to mitochondrial dynamics.