Necropsy findings in a fetus with a 46,XY,dic t(X;21)(p11.1;p11.1).

We report the findings in a fetus terminated because of multiple abnormalities diagnosed on ultrasound, including asymmetry of the limbs, a hypoplastic diaphragm, unilateral duplex kidney with a double ureter, unilateral cystic kidney, and congenital heart disease including total pulmonary atresia. Cytogenetic studies showed an unbalanced translocation of the long arm of the X chromosome to chromosome 21, resulting in a 46,XY,dic t(X;21)(p11.1;p11.1) karyotype. The cytogenetics were confirmed by non-isotopic in situ hybridisation using probes specific to pericentric alphoid repeats. Parental chromosomes were normal indicating this to be a de novo translocation. It is suggested that the inactivation of the long arm of the X chromosome has resulted in an effective monosomy for chromosome 21.