PARACENTRIC INVERSION X(Q21.2Q24) ASSOCIATED WITH MENTAL-RETARDATION IN MALES AND NORMAL OVARIAN-FUNCTION IN FEMALES

We describe a familial paracentric inversion (X)(q21.2 q24) in a family with 2 male and 2 female carriers. The males were mentally retarded and the females were normal with normal ovarian function. It is suggested that a recessive mental retardation (MR) gene was disrupted by one of the inversion breakpoints, although an X-linked MR gene which by chance is linked to the inv(X) could not be ruled out. In the female carriers of the paracentric inversion a random X-inactivation was demonstrated. The normal ovarian function is an exception to the concept of ''critical region'' at Xq13-q26. (C) 1995 Wiley-Liss, Inc.