Twins in Sibships with Klinefelter's Syndrome and the XYY Syndrome

Abstract

SummaryThe frequency of twins and triplets was significantly higher than expected among 56 patients with Klinefelter's syndrome (7.1%), compared with 1.58% in the population (P<0.001), and the frequency of multiple births in the 56 sibships (4.08%) was also significantly higher than expected (P<0.01).One of 15 patients with the XYY syndrome was a twin, and there were 2 twin births among the 53 births in the 15 sibships.