OBJECTIVETo investigate the steroid 21-hydroxylase gene (CYP21) mutations in families with 21-hydroxylase deficiency (21-OHD).

METHODSThe CYP21 gene mutations were detected in four patients with 21-hydroxylase deficiency and their relatives. The genomic DNA of the patients was isolated from whole blood.Two pairs of primers were used to amplify the CYP21 gene. The amplified PCR products were purified by agarose gel and then directly sequenced.

RESULTSSix kinds of mutations were found. In the first family, the patient was a compound heterozygote carrying four different mutations (cluster E6, Q318X, A391T, P459H) onCYP21 gene, three mutations (cluster E6, Q318X, A391T) were on her maternal allele, a novel mutation was found:P459H. It located at codon 459 in exon 10 and changing a proline (CCC) to a histidine (CAC), and A391T was a rare mutation. In the second family, two kinds of mutations were found:cluster E6 and R483W. R483W was also a rare mutation. In the third family, the sequencing of the CYP21 gene of two patients revealed a homozygous T to A transition in codon 172 leading to substitution of isoleucine by asparagine (I172N).

CONCLUSIONSix kinds of mutations were found in three families with 21-hydroxylase deficiency. Using DNA sequencing we have identified a novel mutation (P459H) and two rare mutations (A391T, R483W) of the CYP21 gene. Although microconversion events are the main cause of mutations in the CYP21 gene, random mutations can also be the cause of 21-hydroxylase deficiency.