XXXXY syndrome in a phenotypic male infant with associated cardiac abnormalities

A boy with 49,XXXXY karyotype is described with only mild mental retardation at 18 months. Physical abnormalities included patent ductus arteriosus, undescended testes, small penis, bilateral epicanthal folds, and incurved 5th digits with small middle phalanges. Literature review showed 7 previous cases of XXXXY patients with congenital heart disease. 23% of buccal cells showed 1 sex chromatin body; 26% showed 2 and 11% 3. Autoradiography demonstrated 3 heavily labelled X chromosomes. The heteropyknotic behavior of X Chromosomes in excess of one may provide some measure of protection against excessive numbers of X chromosomes, bence the relatively normal development of some XXXXY patients.