OBJECTIVE: To analyze the frequency of affected patients, rate of parental consanguinity and clinical forms of the disease, according to sex in families with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, classic form (CAH-21-OHD-C). METHODS: 58 families with 79 patients (67 alive and 12 dead) with non-affected parents and at least one affected live patient with an established diagnosis of the disease by molecular analysis were studied. The frequency of affected siblings was evaluated according to Haldane and Hogben techniques by truncated selection. Data about parental consanguinity, frequency of CYP21A2 homozygosis gene mutation, clinical form of the disease and sex distribution were also evaluated. RESULTS: Ten families had parental history of consanguinity and other five had homozygosis in the molecular analysis. The frequency of affected children in the kindred was 23.5%, similar to the 25% expected, but the sample showed a heterogeneous distribution. Among the clinical forms, 56 (70%) patients had the salt wasting form (25 males and 31 females) and 23 (30%) the simple virilizing one (10 males and 13 females) without difference in sex distribution. CONCLUSIONS: These data confirm that CAH-21-OHD-C has an autosomal recessive monogenic inheritance, with a high rate of consanguinity, similar distribution in both sexes, but it has a heterogeneous distribution of cases among the kindred with predominance of the salt wasting form.
adrenal hyperplasia, congenital; steroid 21-hydroxylase; genes, recessive; consanguinity
