Abstract: Objective 　To analyze the clinical and molecular genetic characteristics of a Chinese patient with 17α- hydroxylase/17, 20 Lyase deficiency(17OHD). Methods　Clinical features and laboratory data were collected . Genomic DNA was extracted from leukocytes of peripheral blood of the patient. All eight exons of the CYP17 gene, including the flanking regions of introns, were amplified by PCR. The mutations of the CYP17A1 gene were analyzed by direct sequencing the amplified DNA fragments. Results　The patient was diagnosed as 17OHD according to the clinical presentations , laboratory examinations and CYP17A1 mutation which was identified as a base deletion and a base transversion ( TAC/AA) at codon 329 and caused a missense mutation of Tyr→Lys at this codon and the open reading frame shift following this codon to produce a truncated enzyme without activity site. Conclusions　Through CYP17A1 gene mutation analysis, the clinical diagnosis of 17OHD was confirmed . The alternation of P450c17 structure caused by CYP17A1 gene mutation is the molecular mechanisms of clinical manifestation of the patient.

Key words: 17α- hydroxylase/17, 20 Lyase deficiency, CYP17A1, Mutation