The Martin-Bell syndrome in South Africa.

A national screening programme was introduced in 1980 when the first cases with the Martin-Bell syndrome were diagnosed in South Africa. This survey includes patients from all the major population groups in South Africa. One thousand patients, who include 354 relatives of 21 index cases, were investigated cytogenetically. About 75% of the 354 relatives were either affected males or obligate or possible carriers. The segregation pattern of the fragile site was investigated in 271 offspring of 58 carrier women. At least 30% of the carriers were mildly mentally retarded with most expressing the fragile site. Various other investigations, such as measurements of testes, speech, verbal and IQ evaluations and hormone studies were done on several affected males. No fragile site could be demonstrated in 57 unselected autistic children. The results of this programme show that this syndrome is a common cause of mental retardation and that prevention of mental retardation is possible if all the involved families could be identified.