Small 4p16.3 deletions: Three additional patients and review of the literature.

Wolf-Hirschhorn syndrome is a well-defined disorder due to 4p16.3 deletion, characterized by distinct facial features, intellectual disability, prenatal and postnatal growth retardation, and seizures. Genotype-phenotype correlations based on differently sized deletions have been attempted, and some candidate genes have been suggested. We report on clinical characteristics of three patients with pure interstitial submicroscopic 4p16.3 deletions, ranging in size from 68 to 166 kb, involving WHSCR1 and/or part of WHSCR2, and review published cases with overlapping 4p16.3 losses. The present study highlights a major role of NSD2 gene in the pathogenesis of the WHS main features and predicts that loss-of-function mutations affecting NSD2 gene could result in microcephaly, prenatal and postnatal growth retardation, psychomotor and language delay, and craniofacial features. Absent seizures in all subjects corroborate the suggestion that this specific feature is causally linked with at least one additional causative gene. Finally, we suggest that mir-943 could play a role in the pathogenesis of CHD in some of these patients.

A Small Supernumerary Marker Derived from the Pericentromeric Region of Chromosome 5: Case Report and Delineation of Partial Trisomy 5p Phenotype.

A 17-year-old girl presented with a distinct phenotype mainly featuring craniofacial dysmorphism, including a disproportioned large, round, elongated face; hypertelorism; deep-set eyes with short palpebral fissures; obesity (BMI 37), and a neuropsychiatric disorder with high-functioning autism. Postnatal conventional cytogenetic analyses from peripheral blood revealed a mosaic small supernumerary marker chromosome (sSMC) with a mos 47,XX,+mar[7]/46,XX[43] karyotype. By cenM-FISH technique, the sSMC was identified as a ring derivative of chromosome 5. Metaphase FISH analysis with a set of dedicated probes defined its origin from the pericentromeric region of chromosome 5, including the NIPBL gene at 5p13.2. Such sSMCs, exceedingly rare in the literature, underlie proximal trisomy 5p. In order to delineate a core phenotype of proximal trisomy 5p, we compared our patient's features with those of 6 patients found in the literature with similar der(5) chromosomes. Furthermore, a dozen individuals with 5p13 (micro)duplication syndrome was compared and discussed. We identified highly distinctive craniofacial dysmorphism, obesity, and intellectual disability and/or autism spectrum disorder as typical features of proximal 5p trisomy. In the critical region (band 5p13), the NIPBL gene is likely to be a major determinant of the neurobehavioral phenotype, and its presence at the sSMC level may be relevant to predict clinical outcome.