A patient with 45XO-48XYYY mosaicism.

Many cases of chromosomal mosaicism of the XO/XY type have been described. The phenotype of these patients has shown a wide diversity. In a recent review of 19 published cases in which the XO/XY sex chromosome pattern was established (Jackson, Hoffman, and Makda, 1966), 14 were apparently female and 5 male. The occurrence of XO/XYY mosaicism has been reported less often. Jacobs, Harnden, Buckton, Court Brown, King, McBride, MacGregor, and Maclean (1961) and Cooper, Kupperman, Rendon, and Hirschhorn (1962) each described a phenotypic female with XO/XYY mosaicism, while Trowell and Hamilton (1965) recorded a similar chromosome pattern in a phenotypic male. The present report describes a male pseudohermaphrodite who was found to have XO/XYYY mosaic sex chromosome pattern. An XYYY sex chromosome complement has rarely been observed. Townes, Ziegler, and Lenhard (1965) reported such a pattern in a 5-yearold boy with 48 chromosomes. However, mosaicism of the XO/XYYY type has not been previously described.