High frequency of Q318X mutation in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency in northeast Brazil alta freqüência da mutação Q318X em pacientes com hiperplasia adrenal congênita por deficiência da 21-hidroxilase no nordeste do Brasil

Objetives: Deficiency of 21-hydroxylase is the most common form of congenital adrenal hyperpla- sia (CAH-21OH). The aim of this study was to determine, by allele-specific PCR, the frequency of microconversions of the CYP21A2, in sixteen patients with the classical forms and in 5 patients with the nonclassical (NC) form of CAH-21OH and correlate genotype with phenotype. Methods: Geno- types were classified into 3 mutation groups (A, B and C), based on the degree of enzymatic activity. Screening for 7 microconversions by allele-specific PCR diagnosed 74.3% (n=26) of the 35 unrelated alleles. Results: The most frequent mutations were Q318X (25.7%), V281L (17.1%), I2 Splice (14.3%), I172N (14.3%), and R356W (14.3%). Genotype was identified in 57.1% of the patients. We observed correlation between genotype and phenotype in 91.7% of the cases. Conclusion: The highest fre- quency for Q318X (25.7%) when compared to other studies may reflect individual sample variations in this Northeastern population. Arq Bras Endocrinol Metab. 2009;53(1):40-46.