Abstract
The fragile X syndrome is a recently described entity comprised of X-linked mental retardation, macro-orchidism and a chromosomal fragile site at Xq27. We have studied 50 institutionalized males and 15 non-institutionalized males and found 6 (9.2%) to have this disorder. The frequency of the fragile site ranged from 8-28%. The fragile site was also detected in 4 female obligate carriers (100%) and in 4 potential carriers (67%). Of the 8 carriers, 4 were mentally retarded. The frequency of the fragile X ranged from 4-26% however there was no correlation with age or IQ. Studies of X-inactivation showed that either the normal or the fragile X were inactive. In 5 of 6 females, the normal X was preferentially inactive. Skin fibroblast cultures from 2 subjects who expressed the fragile site in lymphocytes gave 0% and 1% expression of the chromosomal aberration. The clinical findings of the affected males, one of whom was pre-pubertal, showed enlarged testicular volumes. Perseverative speech patterns, low IQ's (30-40), and characteristic facial features including prominent supraorbital ridges and prominent chins were noted. We believe the clinical work-up of any mentally retarded male without microcephaly and other significant somatic defects is incomplete unless the exclusion of the fragile X chromosome has been made. We further suggest that females with any degree of mental retardation, especially mild, should be considered for such studies.
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Carpenter, N., Lelchtman, L. & Say, B. 760 STUDIES ON THE FRAGILE X SYNDROME IN SUBJECTS WITH MENTAL RETARDATION OF UNKNOWN ETIOLOGY. Pediatr Res 15 (Suppl 4), 560 (1981). https://doi.org/10.1203/00006450-198104001-00729
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DOI: https://doi.org/10.1203/00006450-198104001-00729