Objective: To report the clinical characteristics, biochemical profiles, diagnosis and treatment of one Chinese pedigree with glucocorticoid-remediable aldosteronism (GRA) and to study its molecular mechanism.
Methods: Plasma and urinary aldosterone, cortisol and plasma renin activities were dynamically tested and diagnostic therapy with dexamethasone was undergone in 3 affected subjects. Long-distance PCR as well as DNA sequencing were applied to detect the fusion gene in this pedigree.
Results: In this GRA pedigree, there were 4 affected subjects who had hypertension, hypokalemia and low basic and provoked renin activity. Three patients were given dexamethasone treatment, and had a significant decrease in plasma aldosterone concentrations (PACs) (from 192 +/- 9 ng/L to 87 +/- 7ng/L, P < 0.05) after 5 days. Among them, one patient (II -3) responded quite satisfactorily to the therapy, with serum K(+) rising from baseline value of 2.5 to 2.9, 3.8 and 4.15 mEq/L on the 10th, 28th and 35th days after treatment respectively. Three weeks later, his blood pressure decreased from its original level of 146.3 +/- 1 0.7/94.6 +/- 5.3 mm Hg to 138.3 +/- 3.1/87.3 +/- 6.1 mm Hg (P < 0.05). The other 2 members (III -2 and III -4) showed modest improvement although their PACs decreased significantly. Using long-distance PCR, we found a 3.9 kb band in all 4 affected individuals, which was absent in 5 unaffected members from this pedigree or 8 patients with aldosterone-producing adenoma (APA) or idiopathic hyperaldosteronism (IHA). By DNA sequence analysis, we found that the breakpoint of "unequal crossing-over" is both within intron 2 of the 11beta-hydroxylase gene (CYP11B1) and the aldosterone synthase gene (CYP11B2).
Conclusions: The excess of mineralocorticoid in patients with GRA can be inhibited by exogenous glucocorticoids. The fusion gene resulting from unequal crossing-over between the 11beta-hydroxylase gene and the aldosterone synthase gene is the pathogenesis of this Chinese GRA pedigree.