Extra dicentric 15 pter leads to q21/22 chromosomes in five unrelated patients with a distinct syndrome of progressive psychomotor retardation, seizures, hyper-reactivity and dermatoglyphic abnormalities.

Five unrelated patients with a supernumerary chromosome derivative of chromosome 15 are described. The clinical findings in the present series of cases show a gross concordance with the data previously reported in subjects with similar aberrations and allow the delineation of a distinct syndrome. Although undetermined variation in the structure of these extra chromosomes may contribute significantly to phenotypic heterogeneity, the patients display a rather common constellation of findings, which include: absence of major malformations, mental and developmental retardation, seizures, hypotonia, behavioural disturbances, and reduced total ridge count on fingertips. Patients with partial trisomy 15q- resulting from dicentric chromosomes bear little resemblance to patients carrying 15q- chromosomes arising de novo or due to unbalanced translocations.