Clinical, cytological, and biochemical investigations in a case of an XX male.

Lymphocytes and fibroblasts of an XX male were investigated to evaluate the etiology of this trait. DNA extracted from lymphocytes was digested with restriction endonucleases to probe for male specific DNA. There was no indication of such DNA fragments. The X-linked steroid sulfatase showed an activity of female controls while H-Y antigen was found in concentrations comparable to male controls. Cytological examinations excluded a mosaic between 46,XX and 46,XY cells. With the "high resolution banding" technique no evidence was found for a chromosomal aberration in our patient. It is therefore concluded that a "de novo" gene mutation leading to male development is the most suitable explanation for the present case of an XX male.