The 48, XXXX/49,XXXXY/49,XXXX,i(Yq) mosaicism in a 3-year-old boy from a twin pregnancy.

A 3-year-old boy from twin pregnancy with the features of marked dystrophia from birth, deficient growth, considerable retardation of physical and mental development, numerous somatic defects, suspected congenital heart disease, and hypoplastic external genitalia, is reported. The 48,XXXX/49,XXXXY/49,XXXX,i(Yq) karyotype was diagnosed. The boy's brother, normally developed, had a 46,XY karyotype. It was found on the basis of serologic findings that the brothers were dizygotic twins.