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

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.