Subtelomeric 6p monosomy and 12q trisomy in a patient with a 46,XX,der(6)t(6;12)(p25.3;q24.31) karyotype: Phenotypic overlap with Mutchinick syndrome.

We report on a patient with partial monosomy 6p and partial trisomy 12q identified by fluorescent in situ hybridization (FISH) and array-based comparative genomic hybridization (aCGH). She had a complex phenotype characterized by mental retardation (MR), psychomotor developmental delay, speech disorder, hypertelorism, eye anomalies, hearing loss, low-set malformed ears, thin upper lip, heart defect, clinodactyly, pes valgus, and skeletal anomalies. There is phenotypic overlap between our case and Mutchinick syndrome. This is the first report of a combined partial monosomy 6p and partial trisomy 12q due to an unbalanced translocation between subtelomeric regions of these chromosomes.

Cognitive functions in neurofibromatosis type 1 patients and unaffected siblings.

Attention, learning, and perceptual problems have been reported at various degrees and rates in neurofibromatosis type 1 (NF1). We aimed to define the cognitive profiles frequently associated with NF1. Children and adolescents with NF1 (n=58) were tested using Wechsler Intelligence Scales for Children-Revised (WISC-R), Judgment of Line Orientation, and Bender Visual-Motor Gestalt tests. Comparison groups were unaffected siblings of NF1 patients (n=20), children with attention deficit and hyperactivity disorder (ADHD, n=40), and normal children (n=40). No difference was found between familial or sporadic NF1 cases. Seventeen/58 (29%) of NF1 cases had a full scale IQ<70. The subgroup of NF1 patients with full scale IQ>80 (n=27) scored lower in WISC-R subtests measuring visual perception when compared to a healthy control group of similar intelligence, and lower in arithmetic but better in Bender-Gestalt and Judgment of Line Orientation tests when compared to an ADHD group of similar intelligence. These results indicate a high prevalence of mental retardation in a clinical NF1 series. NF1 patients who have normal intelligence may have impaired visual perception, but their visual perceptual problems are less than in ADHD. The tendency of unaffected siblings of NF1 patients to have mildly but consistently low test scores compared to healthy controls needs to be studied further for underlying genetic or environmental factors.

Molecular genetic analyses in neurofibromatosis type 1 patients with tumors.

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders. NF1 is clinically characterized by neurofibromas, pigmentation anomalies, and an increased risk of malignant tumors. The NF1 gene product, neurofibromin, has a GTPase-activating protein domain (GRD) that interacts with the Ras protein, which is crucial in regulating signal transduction and cell proliferation/differentiation. We performed mutation analyses in the NF1-GRD region (exons 21-27a) and in exons 4b, 16, 29, and 37, and intron 28 in 17 NF1 patients with tumors. We identified a large deletion in the NF1 gene in a patient with a rhabdomyosarcoma as well as a variation in intron 22 in a patient with an optic glioma. We also found a 4-base pair deletion in another patient with optic glioma. In addition, allelic loss of the NF1 locus was shown in a pilocytic astrocytoma. Functional analyses of mutations in the NF1 gene may provide further insights into the pathogenesis of NF1 tumors.

Familial segmental neurofibromatosis.

Segmental neurofibromatosis is considered to be the result of postzygotic NF1 gene mutations. We present a family in which the proband has generalized neurofibromatosis 1, whereas members of previous generations manifest segmental skin lesions. All, including the clinically asymptomatic grandmother, carry the same haplotype. This is the only case in the literature in which a parent with segmental skin findings has a child with full-blown neurofibromatosis 1 disease. The genetic mechanisms underlying this association are discussed. This family can be further investigated by examination of tissue samples from affected and unaffected sites for mutations.

Hepatic dislocation associated with left-sided congenital diaphragmatic eventration without situs inversus.

A 3-month-old boy with hepatic dislocation and left-sided congenital diaphragmatic eventration without situs inversus is described. From a review of the literature this appears to be a new clinical condition which may be termed incomplete heterotaxy of abdominal viscera.

Molecular analysis of neurofibromatosis type 1 in Turkish families using polymorphic markers.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder characterized by multiple neurofibromas, café-au-lait spots, and Lisch nodules of iris. The NF1 gene is located on chromosome 17q11.2 and encodes an 11-13 kb mRNA containing 60 exons. The NF1 gene product neurofibromin is a large protein of 2818 amino acids which acts as a negative regulator in the ras signal transduction pathway. The disease has a high mutation rate and a wide range of expression. Because of the size and complexity of the gene, the variety of mutations and the need to identify the specific mutation in each family, indirect diagnosis using linked markers has an important part in genetic counseling. We analyzed 10 Turkish families with a total of 28 affected individuals and 34 non-affected relatives using polymorphic sequences, four intragenic and five flanking markers. Intragenic microsatellite markers were highly informative for all families. As a result, prenatal and presymptomatic diagnoses for familial cases are being made available.

Terminal 14q deletion with unbalanced t(Y;14)(q12;q32) translocation.

Terminal deletions of chromosome 14q are very rarely reported. Schneider et al. (2008) reviewed about 20 cases of 14q32 region deletion in a previous article and only three of the cases involved autosomal translocations; however, no sex chromosome translocations were reported. Here we report the clinical findings of a patient with terminal 14q32 deletion derivated from at (Y;14)(q12;q32) translocation.

The role of RELN in lissencephaly and neuropsychiatric disease.

Reelin is an extracellular matrix-associated protein important in the regulation of neuronal migration during cerebral cortical development. Point mutations in the RELN gene have been shown to cause an autosomal recessive human brain malformation termed lissencephaly with cerebellar hypoplasia (LCH). Recent work has raised the possibility that reelin may also play a pathogenic role in other neuropsychiatric disorders. We sought, therefore, to define more precisely the phenotype of RELN gene disruption. To do this, we performed a clinical, radiological, and molecular study of a family in whom multiple individuals carry a chromosomal inversion that disrupts the RELN locus. A 6-year-old girl homozygous for the pericentric inversion 46,XX,inv7(p11.2q22) demonstrated the same clinical features that have been previously described in association with RELN point mutations. The girl's brain magnetic resonance imaging (MRI) findings, including pachygyria and severe cerebellar hypoplasia, were identical to those seen with RELN point mutations. Fluorescence in situ hybridization confirmed that one of the breakpoints of this inversion mapped to within the RELN gene, and Western blotting revealed an absence of detectable serum reelin protein. Several relatives who were heterozygous for this inversion were neurologically normal and had no signs of psychotic illness. Our findings demonstrate the distinctive phenotype of LCH, which is easily distinguishable from other forms of lissencephaly. Although RELN appears to be critical for normal cerebral and cerebellar development, its role, if any, in the pathogenesis of psychiatric disorders remains unclear.