The marker Xq28 syndrome ('fragile-X syndrome') in a retarded man with mitral valve prolapse

Nearly 15% of all X-linked phenotypes are characterized by some degree of mental retardation without dementia. Many of these conditions can be distinguished on clinical grounds because of associated somatic abnormalities. It has long been recognized, however, that mental retardation is more common in males than females and that this excess cannot be explained fully by the recognized X-linked recessive syndromes. Prompted by numerous reports of the familial occurrence of mental retardation in males who had no other phenotypic abnormalities apparent, a diagnosis of 'nonspecific X-linked mental retardation' arose. Expectations that this diagnosis would prove genetically heterogeneous, once sufficiently discriminating techniques were available received support by the recognition of the association of a novel chromosome aberration with a distinctive pleiotropic clinical manifestation in some mentally retarded males. The patient described here is characterized by a secondary constriction of his X chromosome, macro-orchidism, and mild-to-moderate retardation. He had the additional problem, not previously reported in this syndrome, of mitral regurgitation due to mitral valve prolapse.