Further delineation of the clinical picture of trisomy for the distal segment of chromosome 13: report of three cases.

Three cases of partial trisomy for the distal segment of chromosome 13 are reported. Common clinical features included normal birth weight, postnatal asphyxia, convulsions, severe psychomotor retardation, normal growth, and a distinct pattern of dysmorphias consisting of trigonocephalic head with prominent metopic suture, long and markedly curved eyelashes, a stubby nose, increased distance between nose and upper lip, high-arched palate, misshapen ears with virtually absent lobules and prominent anthelices which are curved in a sharp angle, and hemangiomata. Features present in 2 cases were microcephaly, long and narrow fingers with convex nails, and hexadactyly. Two cousins were unbalanced offspring of a large family of carriers of a 9/13 translocation, whereas the third case exhibited a 13p+ chromosome which was formed de novo. The clinical features in the 3 patients are typical of the syndrome due to partial trisomy for the distal segment of chromosome 13 which shows selected and mitigated signs of full trisomy 13.