Two novel mutations in splice donor sites of CYP11B1 in congenital adrenalhyperplasia due to 11 beta-hydroxylase deficiency

We present an in vivo and in vitro study of congenital adrenal hyperplasia in a patient with 11 beta -hydroxylase deficiency. Genetic analysis showed two new base substitutions of CYP11B1, a conservative transition at the las t base of exon 5, and a IVS8+4A-->G transition in intron 8. Difficulties wi th suppressive therapy resulted in severe hypertension. A laparoscopic adre nalectomy was decided which lead to normalization of blood pressure. In vit ro, steroidogenesis by adrenal cells showed no measurable 11 beta -hydroxyl ase activity. Analysis of CYP11B1 mRNA by RT-PCR and sequencing showed expr ession of a mRNA which lacked exon 8, presumably resulting from the intron 8 mutation. In addition a highly truncated mRNA was detected corresponding to exons 1, 2, 8, 9, with the loss of exons 3-7, presumably related to the exon 5 mutation. Western blot analysis showed a shorter CYP11B immunoreacti ve band of 43 kDa, consistent with truncation of exon 8. Thus adrenalectomy in this patient allowed effective treatment of severe hypertension and hel ped to understand the mechanisms of two novel mutations responsible for abe rrant splicing of CYP11B1.