title: Nonspecific X-linked mental retardation I: a review with information from 24 new families.
abstract: Clinical manifestations and other aspects of nonspecific X-linked mental retardation are reviewed using data from the literature and information on affected males in 24 new families ascertained in British Columbia. A great degree of variability was apparent in the mental abilities of affected males. Speech defects, other CNS disorders and minor physical changes such as "big" ears or a highly arched palate were not present in many cases. Evidence for the existence of a clinical entity of mental retardation associated with the fragile site at Xq27 or 28 and macro-orchidism is discussed. Genetic phenomena of reduced penetrance in males and of partial expression in females with respect of X-linked recessive genes are examined. Consideration is given to the question of whether this type of mental retardation is due to X-linked recessive or autosomal dominant sex-limited genes. Most ascertained cases of X-linked mental retardation are from families of northern European extraction. Recommendations are made regarding the diagnosis and counseling of X-linked mental retardation cases.
mesh_terms: D002493:Central Nervous System Diseases / Q000235:genetics; D005260:Female; D005817:Genetic Counseling; D008040:Genetic Linkage; D005819:Genetic Markers; D014644:Genetic Variation; D006801:Humans; D006984:Hypertrophy; D008607:Intellectual Disability / Q000235:genetics* / Q000523:psychology; D008297:Male; D010375:Pedigree; D010641:Phenotype; D012730:Sex Chromosomes / Q000648:ultrastructure; D012737:Sex Factors; D012917:Social Adjustment; D013064:Speech Disorders / Q000235:genetics; D013737:Testis / Q000473:pathology; D014960:X Chromosome / Q000648:ultrastructure
chemical_list: D005819:Genetic Markers