Familial X‐linked mental retardation and fragile X chromosomes in two Swedish families

Abstract
X-linked mental retardation (MR) associated with a fragile X chromosome was found in 2 Swedish families. The fragile X chromosome was demonstrated in 5/5 boys with mental retardation. Clinical data on 4 of these boys are presented. In 1 of the families, the mental retardation was associated with macroorchidism, large hands and large, folded ears. In the other family, macroorchidism was not seen, possibly because the boys were younger. In the other family, macroorchidism was not seen, possibly because the boys were younger. Fragile site X chromosomes were also seen in 3 obligate carriers. A summary of earlier published cases of X-linked MR associated with the fragile X chromosome is given.