Correction: Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

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Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

PURPOSE: Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors. METHODS: A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study. RESULTS: None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del. CONCLUSION: We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.

Inactivation of Cdc42 in neural crest cells causes craniofacial and cardiovascular morphogenesis defects.

Neural crest cells (NCCs) are physically responsible for craniofacial skeleton formation, pharyngeal arch artery remodeling and cardiac outflow tract septation during vertebrate development. Cdc42 (cell division cycle 42) is a Rho family small GTP-binding protein that works as a molecular switch to regulate cytoskeleton remodeling and the establishment of cell polarity. To investigate the role of Cdc42 in NCCs during embryonic development, we deleted Cdc42 in NCCs by crossing Cdc42 flox mice with Wnt1-cre mice. We found that the inactivation of Cdc42 in NCCs caused embryonic lethality with craniofacial deformities and cardiovascular developmental defects. Specifically, Cdc42 NCC knockout embryos showed fully penetrant cleft lips and short snouts. Alcian Blue and Alizarin Red staining of the cranium exhibited an unfused nasal capsule and palatine in the mutant embryos. India ink intracardiac injection analysis displayed a spectrum of cardiovascular developmental defects, including persistent truncus arteriosus, hypomorphic pulmonary arteries, interrupted aortic arches, and right-sided aortic arches. To explore the underlying mechanisms of Cdc42 in the formation of the great blood vessels, we generated Wnt1Cre-Cdc42-Rosa26 reporter mice. By beta-galactosidase staining, a subpopulation of Cdc42-null NCCs was observed halting in their migration midway from the pharyngeal arches to the conotruncal cushions. Phalloidin staining revealed dispersed, shorter and disoriented stress fibers in Cdc42-null NCCs. Finally, we demonstrated that the inactivation of Cdc42 in NCCs impaired bone morphogenetic protein 2 (BMP2)-induced NCC cytoskeleton remodeling and migration. In summary, our results demonstrate that Cdc42 plays an essential role in NCC migration, and inactivation of Cdc42 in NCCs impairs craniofacial and cardiovascular development in mice.

The practice of adult genetics: a 7-year experience from a single center.

The purpose of our study is to familiarize the reader with genetic disorders commonly seen in adults and identify challenges and barriers that limit provision of services. We conducted a retrospective chart analysis of patients seen in the adult Genetics clinics from January 2004 to December 2010 in a metropolitan medical center consisting of an academic private clinic and a county hospital clinic. During the study period, a total of 1,552 patients (n = 1,108 private clinic patients; n = 444 county clinic patients) were evaluated and managed. Of these, 790 and 280 were new patient visits at the private clinic and county clinic, respectively. Approximately 35% (374/1,070) of new patients were seen for cancer-related indications, while neurological indications accounted for approximately 14% (153/1,070) in both clinics. Cardiology-related indications accounted for approximately 13% (145/1,070) of patients, followed closely by chromosomal and syndromic indications for which almost 9% (96/1,070) of new patients were seen. Approximately 8% (90/1,070) of new patients were seen for musculoskeletal indications. We saw increased clinic growth during the study period and found that the most common indications for referral are: (1) Personal/family history of cancer (2) neurological (3) cardiovascular (CV) (4) chromosomal/syndromic and (5) musculoskeletal. A number of challenges were identified, including coordination of services, feasibility of testing, and an overall higher complexity of care with increased clinic scheduling time requirements. Through this review, we demonstrate the demand for adult genetics services and propose some guidelines to address the challenges of management in the adult genetics patient population.

Early-onset severe neuromuscular phenotype associated with compound heterozygosity for OPA1 mutations.

INTRODUCTION: Pathogenic mutations in the OPA1 gene are the most common identifiable cause of autosomal dominant optic atrophy (DOA), which is characterized by selective retinal ganglion cell loss, a distinctive pattern of temporal pallor of the optic nerve and a typical color vision deficit, with variable effects on visual acuity. Haploinsufficiency has been suggested as the major pathogenic mechanism for DOA. Here we present two siblings with severe ataxia, hypotonia, gastrointestinal dysmotility, dysphagia, and severe, early-onset optic atrophy who were found to be compound heterozygotes for two pathogenic OPA1 mutations. This example expands the clinical phenotype of OPA1-associated disorders and provides additional evidence for semi-dominant inheritance. METHODS AND RESULTS: Molecular analysis of the OPA1 gene in this family by Sanger sequencing revealed compound heterozygosity for two mutations in trans configuration, a p.I382 M missense mutation and a p.V903GfsX3 frameshift deletion in both affected siblings. Electron microscopy of a skeletal muscle biopsy of the older sibling revealed dense osmiophilic bodies within the mitochondria. Mitochondrial DNA (mtDNA) content was within normal limits, and electron transport chain analysis showed no deficiencies of the mitochondrial respiratory chain enzymes. Multiple mtDNA deletions were not found. CONCLUSION: Compound heterozygosity of pathogenic OPA1 mutations may cause severe neuromuscular phenotypes in addition to early-onset optic atrophy. While a role for OPA1 in mtDNA maintenance has been discussed, compound biallelic pathogenic OPA1 mutations in our patients did not result in altered mtDNA copy number, mtDNA deletions, or deficiencies of the electron transport chain, despite the severe clinical phenotype.

Pheochromocytoma and Von Hippel-Lindau in pregnancy.

Pheochromocytoma is an infrequent but well-acknowledged primary cause of malignant hypertension in pregnancy. Although the majority of pheochromocytomas are sporadic, those that present as bilateral or multifocal tumors may be a manifestation of a rare cancer susceptibility syndrome, such as Von Hippel-Lindau (VHL). Gravidae with unrecognized pheochromocytoma are at risk for recurrent paroxysmal hypertensive crises with ensuant maternal and fetal risks. To further illustrate the challenges of management of pheochromocytoma and VHL in pregnancy, we present two illustrative cases. In the first, a multigravida presented with an intrauterine fetal demise and malignant hypertension and a concurrent diagnosis of bilateral pheochromocytomas. A missense mutation in exon 3 of the VHL gene was identified, confirming the diagnosis of VHL type 2C. In the second case, a multigravida with a prior diagnosis of VHL syndrome but sporadic follow-up underwent renal and adrenal imaging surveillance as part of her prenatal care. Although she was normotensive and clinically asymptomatic, such imaging enabled the detection of bilateral pheochromocytomas. In summary, in this report we discuss our management in gravidae with pheochromocytoma and VHL, emphasizing current recommendations pertaining to obstetric management, genetic testing, and long-term follow-up.

Severe aortic root dilatation in infantile Marfan syndrome.

Cardiovascular manifestations of Marfan syndrome are associated with increased mortality, especially in the pediatric population. Early recognition is critical to long-term management. We present two cases of genetically defined "classical" Marfan syndrome presenting with severe infantile aortic root dilatation among siblings and discuss options for therapy.

Generalized metabolic bone disease in Neurofibromatosis type I.

Skeletal abnormalities are a recognized component of Neurofibromatosis type I (NF1) but a generalized metabolic bone defect in NF1 has not been fully characterized thus far. The purpose of this study was to characterize at the densitometric, biochemical and pathological level the bone involvement in NF1 patients. Using dual energy X-ray absorptiometry (DXA) we analyzed bone status in 73 unselected NF1 subjects, 26 males and 47 females, mainly children and adolescents (mean age: 16.6 years). In a subgroup of subjects with low bone mass, we measured indices of calcium-phosphate metabolism, bone turnover, and bone density before and after vitamin D and calcium treatment. We found statistically significant and generalized reduction in bone mass with the mean lumbar bone mineral density (BMD) z-score being -1.38+/-1.05 (CI 95% -1.62 to -1.13), and whole body bone mineral content (BMC) z-score -0.61+/-1.19 (CI 95% -0.94 to -0.29), both significantly reduced compared to normal controls (p<.001). PTH was moderately elevated and after 4 months of supplemental therapy with calcium and vitamin D, it decreased to the normal range. However, BMD z-scores did not significantly improve after 2 years of follow-up. Histological analysis of bone samples from NF1 patients revealed substantial alteration of bone microarchitecture due mainly to reduced trabecular bone. Our observations are consistent with a generalized bone metabolic defect due to loss of the function of neurofibromin. Early identification of patients with osteoporosis may permit more timely and aggressive treatments to prevent the likely substantial morbidity associated with increased fracture risk later in life.

A homozygous mutation in MSH6 causes Turcot syndrome.

Heterozygous mutations in one of the DNA mismatch repair genes cause hereditary nonpolyposis colorectal cancer (MIM114500). Turcot syndrome (MIM276300) has been described as the association of central nervous system malignant tumors and familial colorectal cancer and has been reported to be both a dominant and recessive disorder. Homozygous and compound heterozygous mutations in APC, MLH1, MSH2, and PMS2 genes have been reported in five families. Here we describe a nonconsanguineous Pakistani family, including a son with lymphoma and colorectal cancer diagnosed at ages 5 and 8, respectively, and an 8-year-old daughter with glioblastoma multiforme. Both children had features of neurofibromatosis type 1 including atypical café au lait spots and axillary freckling without a family history consistent with neurofibromatosis type 1, familial adenomatous polyposis, or hereditary nonpolyposis colorectal cancer. Mutational analysis was done for MLH1, MSH2, and MSH6 using denaturing high-performance liquid chromatography and sequencing of a blood sample from the daughter. A novel homozygous single base insertion mutation was identified (3634insT) resulting in a premature stop at codon 1,223 in exon 7 of the MSH6 gene. Both parents were found to be heterozygous for the 3634insT mutation. Microsatellite instability testing showed instability in the glioblastoma sample. We report here the first identification of a homozygous mutation in MSH6 in a family with childhood-onset brain tumor, lymphoma, colorectal cancer, and neurofibromatosis type 1 phenotype. Our findings support a role for MSH6 in Turcot syndrome and are consistent with an autosomal recessive mode of inheritance.

Assay validation for identification of hereditary nonpolyposis colon cancer-causing mutations in mismatch repair genes MLH1, MSH2, and MSH6.

Hereditary nonpolyposis colon cancer (HNPCC, Online Mendelian Inheritance in Man (OMIM) 114500) is an autosomal dominant disorder that is genetically heterogeneous because of underlying mutations in mismatch repair genes, primarily MLH1, MSH2, and MSH6. One challenge to correctly diagnosing HNPCC is that the large size of the causative genes makes identification of mutations both labor intensive and expensive. We evaluated the usefulness of denaturing high performance liquid chromatography (DHPLC) for scanning mismatch repair genes (MLH1, MSH2, and MSH6) for point mutations, small deletions, and insertions. Our assay consisted of 51 sets of primers designed to amplify all exons of these genes. All polymerase chain reaction reactions were amplified simultaneously using the same reaction conditions in a 96-well format. The amplified products were analyzed by DHPLC across a range of optimum temperatures for partial fragment denaturation based on the melting profile of each specific fragment. DNA specimens from 23 previously studied HNPCC patients were analyzed by DHPLC, and all mutations were correctly identified and confirmed by sequence analysis. Here, we present our validation studies of the DHPLC platform for HNPCC mutation analysis and compare its merits with other scanning technologies. This approach provides greater sensitivity and more directed molecular analysis for clinical testing in HNPCC.

Catel-Manzke Syndrome: Further Delineation of the Phenotype Associated with Pathogenic Variants in TGDS.

Catel-Manzke syndrome is a rare autosomal recessive disorder characterized by Pierre Robin sequence with hyperphalangy and clinodactyly of the index finger. Recently, homozygous or compound heterozygous pathogenic variants in TGDS have been discovered to cause Catel-Manzke syndrome. Here, we describe a 12-month-old male with molecularly confirmed Catel-Manzke syndrome who presented with Pierre Robin sequence (but without cleft palate) and hyperphalangy, and we compare his phenotype with the seven previously described patients with pathogenic variants in TGDS. Our patient is on the severe end of the phenotypic spectrum, presenting with respiratory complications and failure to thrive. Furthermore, our finding of a homozygous p.Ala100Ser pathogenic variant in our patient supports that it is a common mutation in Catel-Manzke syndrome.

Phenotypic variability of osteogenesis imperfecta type V caused by an IFITM5 mutation.

In a large cohort of osteogenesis imperfecta type V (OI type V) patients (17 individuals from 12 families), we identified the same mutation in the 5' untranslated region (5'UTR) of the interferon-induced transmembrane protein 5 (IFITM5) gene by whole exome and Sanger sequencing (IFITM5 c.-14C > T) and provide a detailed description of their phenotype. This mutation leads to the creation of a novel start codon adding five residues to IFITM5 and was recently reported in several other OI type V families. The variability of the phenotype was quite large even within families. Whereas some patients presented with the typical calcification of the forearm interosseous membrane, radial head dislocation and hyperplastic callus (HPC) formation following fractures, others had only some of the typical OI type V findings. Thirteen had calcification of interosseous membranes, 14 had radial head dislocations, 10 had HPC, 9 had long bone bowing, 11 could ambulate without assistance, and 1 had mild unilateral mixed hearing loss. The bone mineral density varied greatly, even within families. Our study thus highlights the phenotypic variability of OI type V caused by the IFITM5 mutation.

Speech delay and autism spectrum behaviors are frequently associated with duplication of the 7q11.23 Williams-Beuren syndrome region.

PURPOSE: Williams-Beuren syndrome is among the most well-characterized microdeletion syndromes, caused by recurrent de novo microdeletions at 7q11.23 mediated by nonallelic homologous recombination between low copy repeats flanking this critical region. However, the clinical phenotype associated with reciprocal microduplication of this genomic region is less well described. We investigated the molecular, clinical, neurodevelopmental, and behavioral features of seven patients with dup(7)(q11.23), including two children who inherited the microduplication from one of their parents, to more fully characterize this emerging microduplication syndrome. METHODS: Patients were identified by array-based comparative genomic hybridization. Clinical examinations were performed on seven affected probands, and detailed cognitive and behavioral evaluations were carried out on four of the affected probands. RESULTS: Our findings confirm initial reports of speech delay seen in patients with dup(7)(q11.23) and further delineate and expand the phenotypic spectrum of this condition to include communication, social interactions, and repetitive interests that are often observed in individuals diagnosed with autism spectrum disorders. CONCLUSIONS: Array-based comparative genomic hybridization is a powerful means of detecting genomic imbalances and identifying molecular etiologies in the clinic setting, including genomic disorders such as Williams-Beuren syndrome and dup(7)(q11.23). We propose that dup(7)(q11.23) syndrome may be as frequent as Williams-Beuren syndrome and a previously unrecognized cause of language delay and behavioral abnormalities. Indeed, these individuals may first be referred for evaluation of autism, even if they do not ultimately meet diagnostic criteria for an autism spectrum disorder.

Spinocerebellar ataxia type 2 (SCA2) presenting with ophthalmoplegia and developmental delay in infancy.

An 11-year-old boy was evaluated for progressive ataxia, cognitive deterioration, and ophthalmoplegia. The child initially presented with abnormal eye movements at the age of 2 months and was noted to have developmental delay at 6 months. At the age of 7 years, he developed ataxia and cognitive impairment, and subsequently manifested dysphagia and incontinence. The pertinent family history included gait difficulty in the paternal grandmother. At the age of 11, his general physical examination was normal. On neurological examination, he had bilateral external ophthalmoplegia, ataxic dysarthria, dysmetria and tremor in the upper extremities, and marked gait ataxia. An ophthalmological evaluation showed no evidence of pigmentary retinopathy. Brain MRI demonstrated cerebellar, brainstem, and cerebral atrophy. An ataxia panel showed 62 repeats in one allele of the SCA2 gene. Most cases of spinocerebellar ataxia type 2 (SCA2) present between 20 years and 40 years, and affected individuals typically have between 34 and 57 CAG repeats. Neonatal cases of SCA2 have been reported in individuals with over 200 CAG repeats. Childhood SCA2 has been reported previously in two patients but not described clinically. This case broadens the spectrum of the clinical features of infantile-onset SCA2 and highlights the importance of considering this diagnosis in infants and children.