[Sex linked mental deficiency, unusual facies, macroorchidism and fragile site on chromosome X (author's transl)].

The association of mental deficiency, macroorchidism, and a fragile site on chromosome X [fra (X)(q28) is reported in a 13-year-old boy who also exhibits a peculiar facies reminescent of trisomy 8. This particular facies is considered part of the clinical syndrome associated with the fra(X)(q28). The fra(X)(q28) was not found in the mother nor in two normal sibs of the propositus. The significance of the marker is discussed in view of two hypotheses, close linkage between pathological gene(s) and the fra(X)(q28) and faulty transcription of the gene(s) beyond the tra(X)(q28).