Mira Irons

BACKGROUND: The Smith-Lemli-Opitz syndrome (frequency, 1:20,000 to 1:40,000) is defined by a constellation of severe birth defects affecting most organ systems. Abnormalities frequently include profound mental retardation, severe failure to thrive, and a high infant-mortality rate. The syndrome has heretofore been diagnosed only from its clinical presentation. METHODS: Using capillary-column gas chromatography-mass spectrometry, we measured the sterol composition of plasma, erythrocytes, lens, cultured fibroblasts, and feces from five children with the syndrome (three girls and two boys). RESULTS: Plasma cholesterol levels were abnormally low (8 to 101 mg per deciliter [0.20 to 2.60 mmol per liter]) in every patient, being well below the 5th percentile for age- and sex-matched controls. Concentrations of the cholesterol precursor 7-dehydrocholesterol (cholesta-5,7-dien-3 beta-ol), which was not detectable in most of our controls, were elevated (11 to 31 mg per deciliter) more than 2000-fold above normal and were similar to the levels of cholesterol in all tissues from all patients. An isomeric dehydrocholesterol with a structure similar to that of 7-dehydrocholesterol was also detected. CONCLUSIONS: The combination of abnormally low plasma cholesterol levels and a high concentration of the cholesterol precursor 7-dehydrocholesterol points to a major block in cholesterol biosynthesis at the step in which the C-7(8) double bond of 7-dehydrocholesterol is reduced, forming cholesterol. The block may be sufficient to deprive an embryo or fetus of cholesterol and prevent normal development, whereas the incorporation of 7-dehydrocholesterol into all membranes may interfere with proper membrane function.

Research has implicated mutations in the gene for neurexin-1 (NRXN1) in a variety of conditions including autism, schizophrenia, and nicotine dependence. To our knowledge, there have been no published reports describing the breadth of the phenotype associated with mutations in NRXN1. We present a medical record review of subjects with deletions involving exonic sequences of NRXN1. We ascertained cases from 3,540 individuals referred clinically for comparative genomic hybridization testing from March 2007 to January 2009. Twelve subjects were identified with exonic deletions. The phenotype of individuals with NRXN1 deletion is variable and includes autism spectrum disorders, mental retardation, language delays, and hypotonia. There was a statistically significant increase in NRXN1 deletion in our clinical sample compared to control populations described in the literature (P = 8.9 x 10(-7)). Three additional subjects with NRXN1 deletions and autism were identified through the Homozygosity Mapping Collaborative for Autism, and this deletion segregated with the phenotype. Our study indicates that deletions of NRXN1 predispose to a wide spectrum of developmental disorders.

BACKGROUND: Mutations in the PTEN gene cause two disorders that predispose to cancer, Bannayan-Riley-Ruvalcaba and Cowden syndromes. Some patients with a PTEN mutation have only macrocephaly and autism, but they may still be at risk for neoplasms. Vascular anomalies occur in patients with a PTEN mutation, but they have not been systematically studied or precisely defined. METHOD: We analysed the clinical and radiological features of the vascular anomalies in 26 patients with PTEN mutations who were either seen or had their medical records reviewed at Children's Hospital Boston. RESULTS: All 23 patients who had their head circumference measured were macrocephalic, and all 13 male patients who were fully examined had penile freckling. Vascular anomalies were found in 14/26 (54%) of patients: 8/14 (57%) had multiple lesions and 11/13 (85%) who had cross-sectional imaging had intramuscular vascular lesions. Radiographic studies showed that 12/14 (86%) were fast-flow vascular anomalies, and angiography typically showed focal segmental dilatation of draining veins. Excessive ectopic fat in the vascular anomalies was present in 11/12 (92%) of patients on CT or MRI. Intracranial developmental venous anomalies (DVAs) were found in 8/9 (89%) of patients who had brain MRI with contrast. CONCLUSIONS: Vascular anomalies in patients with a PTEN mutation are typically multifocal intramuscular combinations of fast-flow channels and ectopic fat. Cerebral DVAs are very common. PTEN mutational analysis should be considered for all macrocephalic patients with fast-flow vascular anomalies or multiple intracranial DVAs.