CYTOGENETIC ANALYSIS OF A BOY WITH THE XXXY SYNDROME: ORIGIN OF THE X-CHROMOSOMES
A 3-year-old boy with radio-ulnar synostosis and mild mental retardation was found to have a 48/XXXY chromosome constitution in blood and skin cultures without evidence of mosaicism. Autoradiography of the cultured cells identified two late-labeling X-chromosomes. His buccal smear revealed double and single sex chromatin bodies. The patient and his family were studied for segregation of Xg blood types which are controlled by X-linked genes. This revealed the father to be Xg(a+), a positive hemizygote; the mother Xg (a-) was homozygous negative; and the proband was Xg(a-). These findings suggest that the three X-chromosomes of the proband came from his mother. It is proposed that nondisjunction occurred at both the first and second meiotic divisions of oogenesis, producing a triple-X (XXX) ovum which was then fertilized by the paternal Y-bearing sperm. This communication represents the first reported case of the XXXY syndrome in which informative cytogenetic evaluation has been obtained.