Novel missense mutations, GCC [Ala306]- > GTC [Val] and ACG [Thr318]- > CCG [Pro], in the CYP11B1 gene cause steroid 11beta-hydroxylase deficiency in the Chinese.

OBJECTIVE: Steroid 11beta-hydroxylase (CYP11B1) deficiency, an autosomal recessive inherited disease, accounts for 5-8% of congenital adrenal hyperplasia (CAH). It is mainly caused by mutations of nucleotide substitutions in the coding region. PATIENTS AND METHODS: The study reports on a 9-year-old Chinese boy who presented with a bone age of 16 years, an enlarged penis, an accelerated growth rate since early childhood and hypertension (160-170/100-110 mmHg) for 3 years. Because it shares 95% sequence homology with aldosterone synthetase (CYP11B2), we developed gene-specific primers for differential PCR amplification of the CYP11B1 gene. The secondary PCR products of nine exons of the CYP11B1 gene were then subjected to single-strand conformation polymorphism (SSCP) analysis and DNA sequencing. The serum hormone levels were also determined.
RESULTS: We found that the boy diagnosed with CAH due to 11beta-hydroxylase deficiency carried mutations of A306V (GCC- > GTC) and T318P (ACG- > CCG) in two respective chromosomes. The hormone assay showed that the 11-deoxycortisol level was higher (667 nmol/l) than normal and was further increased after ACTH stimulation (1206 nmol/l).
CONCLUSIONS: These two mutations have not previously been described in the CYP11B1 gene. The discovery of these two novel mutations increases our knowledge of CAH caused by 11beta-hydroxylase deficiency.