CYP21 analysis and phenotype/genotype relationship in the screened population of the Italian Emilia-Romagna region

OBJECTIVES We have genotyped the patients with congenital adrenal hyperplasia due to 21‐hydroxylase deficiency identified from March 1980 to December 1997 through a combined program of neonatal screening and case survey in the Emilia–Romagna Region (Italy). We have also analysed retrospectively the possible advantages of genotypical neonatal classification. DESIGN A ‘phase A’ of screening and clinical monitoring (March 1980–September 1983 and March 1991–December 1997) and a ‘phase B’ of clinical monitoring only (October 1983–February 1991) were taken into account. PATIENTS A total of 61 patients (20 salt wasting, nine simple virilizing and 32 nonclassical forms) were genotyped, HLA typed and hormonally tested to understand better the genotype/phenotype relationship and the epidemiology and geographical distribution of associated mutations. The fully genotyped patients were classified into four mutation groups according to the degree of enzymatic activity (‘null’ and ‘A’ to ‘C’). RESULT The most frequent genotype alterations were deletion (24.1% classical, 3.3% nonclassical forms), large gene conversion (9.2% classical, 1.7% nonclassical forms), In2 splice (27.7% classical, 15.0% nonclassical forms), I172N (5.5% classical, 10.0% nonclassical forms), V281L (3.7% classical, 43.3% nonclassical forms), P453S (5.0% nonclassical forms). A significant difference (χ2 = 5.101; P