PMID: 7992687Jan 1, 1994Paper

Fragile X syndrome

Advances in Pediatrics
R Laxova


1. Fragile X syndrome is defined by the combination of a characteristic phenotype, cognitive impairment, the presence of a fragile site (gap) detectable in folate-free culture medium on Xq27.3 called FRA X A, and transcriptional inhibition, through overmethylation, of an mRNA protein-binding gene called FMR-1. 2. It is inherited in an atypical X-linked dominant way and affects about 1 in 1000 males and 1 in 2000 females; about 1 in 700 females is a carrier. 3. A characteristic but subtle phenotype includes an elongated face and mandible, large ears, macrocephaly with bizygomatic pinching, soft skin, inconsistent mitral valve prolapse, macroorchidism, mildly shortened stature in adulthood, and characteristic behavior that may resemble autism and attention deficit disorders. Intellectual impairment in affected individuals varies from mild to severe, with a majority of affected males within the moderate range of cognitive disability. Twenty percent of males with the mutation are phenotypically and intellectually unaffected. They ae called transmitting males. 4. Female heterozygotes may be indistinguishable from the general population, or they may have subtle physical signs or both physical and intellectual impairment. 5. Sensory m...Continue Reading

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