Molecular and clinical study on homozygous or heterozygous large deletion of CYP21A2 gene in 21-OHD patients

Abstract

Objective: To explore the relationship between homozygous or heterozygous large deletion of CYP21A2 gene and clinical manifestation in 21-hydroxylase deficiency (21-OHD) patients. Methods: The records of 100 patients with 21-OHD were collected between June 2016 and December 2017 in Peking Union Medical College Hospital. Large deletion of CYP21A2 gene was detected by multiplex ligation probe amplification (MLPA). The biochemical results and clinical symptoms of patients with homozygous or heterozygous large deletion were analyzed in order to investigate the influence of complete or single allele deletion of CYP21A2 gene on 21-OHD patients. Results: Large deletion of CYP21A2 gene was detected in 33 patients by MLPA, including 13 males and 20 females, with an median age of 10 (6,16) years. Two of them had simultaneous deletions of two alleles. Among 31 patients with heterozygous deletion, 16 were combined with gene mutations that severely affected 21-hydroxylase enzyme activity (I2G and Q318X), 15 with mutations that retained part enzyme activity (I172N and P30L). Two patients with complete deletion of CYP21A2 gene had no significant difference in biochemical and clinical manifestations compared with those with single allele deletion combined with another gene mutation that severely affected enzyme activity. Both kinds of patients above were manifested as severe salt-wasting type. Patients with a single allele deletion and a mutation retaining part enzyme activity were manifested as mild simple-viralizing type. Conclusion: Large deletion of CYP21A2 gene could appear in 21-OHD patients and the phenotype is similar to that of salt-wasting patients with heterozygous large deletion.