Genetics of X-Linked Mental Retardation

摘要: Mental retardation (MR) is defined as an overall “intelligence quotient” (IQ) <70, associated with functional deficits in adaptive behaviour (such daily-living skills, social skills and communication), onset before 18 years (1). Approximately 2–3% of the population have intelligence quotient <70 (2,3) at least 0.3% individuals are severely handicapped (IQ <50) (Table 1), yet a cause for mental established less than half all cases (4). The underlying causes MR extremely heterogeneous 2). In addition to multiple nongenetic factors that act prenatally or during early infancy brain injury, chromosomal anomalies, such aneuploidy syndromes, example, Down syndrome, microdeletion Prader—Willi, Angelman, Miller—Dieker, Smith—Magenis, Williams represent important genetic MR. Recent studies suggest rearrangements affect telomeric regions autosomes, not detectable by conventional cytogenetic analysis, may account up 7% moderate severe (5,6). Genetic be involved one retarded patients (7). Some disorders which gene identified relatively significant numbers families, fragile X syndrome (which affects approx 1/4000–6000 males) (8,9) Rett (1/10,000–15,000 girls) (10),but our knowledge these monogenic still far from complete.