Clinical manifestations of chromosome 21 interstitial deletion: report of four cases.

Chromosome 21 is the smallest human chromosome; it contains 1.7% of the human genome, or about 54,000 kb. Multiple abnormalities have been observed in patients with a deletion of the long arm of chromosome 21. Phenotypic variability between cases involving different deletions of 21q have been described. We report four cases of deletion (21)(q11.2-q22.1). Three of the reported cases are familial, involving a mother and her two sons, and one is de novo. All cases had mild mental retardation, antimongolian slants, long philtrum, and protruding tongue as well as open mouth. Hypertonia was noted when each was young. Arachnoid cyst, cerebral dysfunction, thalassemia minor, and growth hormone deficiency were found in the de novo case. This is the first report of chromosomal deletion (21)(q11.2-q22.1) in the Taiwanese population.