Autosomal trisomy in a chimpanzee: resemblance to Down's syndrome

An infant chimpanzee (Pan troglodytes) with clinical, behavioral, and cytogenetic features similar to those in Down's syndrome is described. The infant shows retarded growth rate, congenital abnormalities, retarded neurologic and postural development, epicanthus, hyperflexibility of the joints, muscle hypotonia, and trisomy of a small acrocentric chromosome.