Skewed X inactivation in Lesch–Nyhan disease carrier females

X chromosome inactivation (xci) ratios of normal females can range from a highly skewed ratio of 0:100 to a 50:50 ratio. in several x-linked disorders, female carriers present skewed x inactivation. hypoxanthine–guanine phosphoribosyltransferase (hprt) deficiency is an x-linked disorder. males are affected and present with the complete lesch–nyhan disease (lnd) or with a partial phenotype (lesch–nyhan variant, lnv). female carriers are usually asymptomatic. the aim of the present study was to analyze the xci pattern of hprt-deficiency carrier females. as a group, 75% of hprt-deficiency carrier females presented skewed xci. moreover, skewed xci is significantly more frequent in lnd carriers (83%) than in lnv (0–50%, depending on the phenotype severity). the ratios of the preferentially inactivated allele of carrier females were significantly higher than the ratios of the preferentially inactivated allele of noncarrier females (89.4±15, n=52 vs 65.2±12, n=52; p<0.0001). for carrier diagnosis, the presence of skewed xci presents a sensitivity of 75% with a specificity of 85%. in lnd families, the presence of skewed xci is more sensitive for carrier diagnosis than in lnv families; however, we believe that this test is not accurate for carrier diagnostic purposes.