We analyzed large gene deletion or conversion and the 9 most common micro mutations in the CYP21A2 gene by polymerase chain reaction; micro mutation of I172N and heterozygous large gene deletion or conversion were detected leading to the diagnosis of nonclassical 21-OHD. Here, CYP21A2 is linked to classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency.