Phenotypic and Cytogenetic Variety of Pure Partial Trisomy

Duplications of chromosome 16p are often the products of unbalanced maternal reciprocal translocations and consequently the phenotype of patients is not typical of pure partial trisomy 16p. R-banding and fluorescence in situ hybridization (FISH) in our patients were in favour of de novo pure partial trisomy of 16p. Furthure clinical and paraclinical analysis of our three cases in addition to a review of literature and analysis of published clinical and cytogenetic data on five cases of pure partial duplications of chromosome 16p reported until now lead to the delineation of three groups of duplications. Patients with short proximal 16p11~p12 euchromatic duplication considered as "silent" duplication and no clinical anomaly are included in the first group. The second group with a larger 16p11-p12~p13 duplication is caracterised by a particular phenotype including severe mental retardation, dysmorphism, variable malformations and recurrent infections. The third group has terminal 16p13-pter duplication and is not well defined to date. Based on our cases and reported cases of pure partial trisomy of 16p in the literature we propose diagnostic measures in case of an elongated 16p chromosome encountered in prenatal chromosome analysis.