A clinical, cytogenetic and familial study of 307 mentally retarded, institutionalized, adult male patients with special interest for fra(X) negative X‐linked mental retardation

Abstract
In this study we report the results of a systematic etiological, clinical genetic study in 307 institutionalized mentally retarded adult males. Special attention is paid to the nosology of X‐linked mental retardation. During the survey 63 males with one or more ‘Martin Bell’‐like features were identified in whom repetitive fragile Xq27–3 screenings were negative. In 13 of them, belonging to 9 different families, pedigree data were compatible with X‐linked inheritance. This finding confirms the existence of one (or more) forms of fra(x) negative mental retardation with ‘Martin Bell’‐like features.