Structural abnormalities of the Y chromosome and abnormal external genitals.

Three infants with different types of Y-chromosome anomalies, including short- and/or long-arm deletion and mosaicism, are reported. The karyotypes of these patients were: 45,X/46, X,del(Y)/47,X,del(Y), del(Y) on peripheral lymphocytes and 45,X/46,2, del(Y) on gonadal tissue (case 1), 45,X/46X,del(Y) (case 2), and 45,X/46X,r(Y) (case 3). In case 1 the euchromatic segment on the deleted Y was distinctly larger than that of the father's Y. The three infants had no gross phenotypic anomalies except ambiguous genitals and low birth weight, and they were small for date. The histologic diagnosis in two of them was mixed gonodal dysgenesis (cases 1 and 2). The relationship between structural abnormalities of the Y chromosome and ambiguous genitals as well as male-determining factors is discussed.