Liddle's syndrome, an underrecognized entity: a report of four cases, including the first report in black individuals.

Liddle's syndrome, a rare cause of hypokalemic hypertension, is characterized by a renal tubular sodium channel defect resulting in excessive sodium absorption and concomitant potassium wasting. In this disorder, although the clinical manifestations resemble primary aldosteronism, serum and urine aldosterone are suppressed. The syndrome is transmitted in an autosomal dominant pattern. It has been reported previously in white and oriental populations but not in the black individuals. We identified four patients (two of whom are black) in our nephrology clinic, with severe hypokalemic hypertension not correctly diagnosed for several years. All patients underwent an extensive work-up for secondary hypertension because of persistent severe hypertension (average blood pressure, 210/130 mm Hg) despite high-dose multi-drug therapy. Primary aldosteronism was excluded because of low serum aldosterone. Cushing's syndrome, pheochromocytoma, renal artery stenosis, and enzymatic deficiencies of cortisol synthesis (11 beta-hydroxylase, 17 alpha-hydroxylase, 5 beta-reductase, and 11 beta-hydroxysteroid dehydrogenase) were ruled out with extensive endocrine and radiologic studies. Once the diagnosis of Liddle's syndrome was suspected, all patients were treated with either triamterene or ameloride, with resolution of hypokalemia and correction of hypertension occurring within 5 to 7 days. Our findings suggest that Liddle's syndrome can occur in the black population. Although the actual incidence of this syndrome remains unknown, it may be significantly more common than we are led to believe since it is inherited in a Mendelian pattern. Whether there is a subset of low-renin, salt-sensitive black hypertensive patients who have the same or similar sodium channel defect remains to be elucidated.