Marker X Chromosomes, Mental Retardation and Macro-Orchidism

Abstract

To the Editor: In 1977 Sutherland wrote a letter in the Journal ¹ describing a fragile site on the long arm of the X chromosome in X-linked mental retardation (Renpenning's syndrome) when the cells were cultured in a special medium. This fragile site could also be found in reduced frequency in a proportion of the obligate carrier females. We had previously described a number of families with X-linked mental retardation,^{2 3 4} noting the lack of associated physical abnormalities, and had then described two further families⁵ in which the affected males had unexplained macro-orchidism.We decided to re-examine a number of our families . . .