PPP2R2C, a gene disrupted in autosomal dominant intellectual disability.

Intellectual disability (ID) comprises a vast collection of clinically diverse and genetically heterogeneous disorders characterized primarily by central nervous system defects of varying severity with or without additional dysmorphic, metabolic, neuromuscular or psychiatric features. Much progress has been made to elucidate the genetic causes for ID, especially on the X-chromosome. In order to identify autosomal genes involved in ID, patients with a balanced chromosomal rearrangement are a valuable source since the breakpoints may disrupt or deregulate a candidate ID gene(s).

Dosage-dependent severity of the phenotype in patients with mental retardation due to a recurrent copy-number gain at Xq28 mediated by an unusual recombination.

We report on the identification of a 0.3 Mb inherited recurrent but variable copy-number gain at Xq28 in affected males of four unrelated families with X-linked mental retardation (MR). All aberrations segregate with the disease in the families, and the carrier mothers show nonrandom X chromosome inactivation.

Congenital diaphragmatic hernia is part of the new 15q24 microdeletion syndrome.

The recurrent microdeletion 15q24 syndrome is rare with only 5 cases reported thus far. Here we describe an additional patient with this deletion, presenting with many features common to this syndrome, including developmental delay, loose connective tissue, digital and genital anomalies and a distinct facial gestalt. Interestingly, in addition, this patient has a large congenital diaphragmatic hernia, as was described in one other patient with a 15q24 microdeletion, indicating that this feature might be part of the syndrome.

Novel GJA1 mutations in patients with oculo-dento-digital dysplasia (ODDD).

Oculo-dento-digital dysplasia (ODDD) is an autosomal dominant disorder characterized by developmental anomalies of the face, the eyes, the limbs and the teeth. Patients with ODDD usually present with complete syndactyly of the fourth and fifth fingers (type III syndactyly), ocular changes, abnormalities of primary and permanent dentition and specific craniofacial malformations. Mutations in GJA1, a gene that encodes the gap junction protein connexin 43, are responsible for ODDD.

Cri du chat syndrome: changing phenotype in older patients.

The cri du chat syndrome or 5p deletion syndrome is a well-delineated clinical entity and has an incidence of 1/50,000 in newborn infants. A de novo deletion is present in 85% of the patients. Ten to 15% are familial cases with more than 90% due to a parental translocation and 5% due to an inversion of chromosome 5.

A study of the cognitive and psychological profile in 16 children with congenital or juvenile myotonic dystrophy.

We report data on intelligence and on possibly associated psychopathology in 16 children and adolescents, between 7 and 18 years of age, with congenital or juvenile myotonic dystrophy. We found that all the subjects have an intelligence level below the population mean, four of them in the mentally retarded range. An unexpected number of subjects are in the clinical range on the Child Behavior Checklist.

Fountain syndrome: further delineation of the clinical syndrome and follow-up data.

We present five patients with the clinical diagnosis of Fountain's syndrome, an autosomal recessive entity with mental retardation, deafness, skeletal abnormalities and coarse face with full lips as cardinal features and review all cases reported so far. We report two new isolated cases, and present follow-up data on three previously reported patients. The clinical features of all these patients are presented to further delineate the clinical picture and the natural course of this rare syndrome.