Genetic and endocrine findings in a 48,XXYY male.

Characteristics of a 16-yr-old male with a 48,XXYY karyotype are presented; this chromosome constitution was demonstrated consistently in four tissue studied. Basal gonadotropins were elevated, and serum testosterone varied between 3.2-4.0 ng/ml. A pronounced rise was observed in LH after LRH administration with a lesser rise of FSH. The testis displayed hyperplasia of the interstitial cells, tubular atrophy, absent spermatogenesis with preservation of some Sertoli cells, and peritubular fibrosis. The phenotypic, behavioral, endocrine and pathological features of this patient are compared with those found in males with the 47,XXY and 47,XYY syndromes. The 48,XXYY phenotype may result from compounding effects of the additional X and Y chromosomes.