Abstract

We present a male patient with Down-Turner mosaicism (45,X/46,X,+21/47,XY,+21) and review 27 similar cases reported so far. Clinical features of Down's syndrome were present in all cases, whereas a combination of features of both Ullrich-Turner syndrome and Down's syndrome was reported in 61% of the patients. However, one has to bear in mind that several stigmata of Ullrich-Turner syndrome can also be present in patients with Down's syndrome and vice versa. In most of the patients two different cell lines were encountered, although cases with one, three, and even four different cell lines have been reported. Of 28 patients, 21 showed female external genitalia, four were phenotypically male, and three showed ambiguous genitalia. Only six patients (21%) carried a Y chromosome, which is far less than expected.