Selective hypoaldosteronism in infancy. Report of a case.

A 10-week-old female infant had anorexia, failure to thrive, and dehydration. Hyponatremia and hyperkalemia were found, along with urinary salt loss and increased plasma renin activity. Plasma deoxycorticosterone, corticosterone, and urinary 18-hydroxycorticosterone levels were increased. The plasma aldosterone levels were inappropriately reduced given the degree of sodium depletion present, while urinary aldosterone concentrations were persistently low. These are characteristic findings of an enzymatic defect in the synthesis of aldosterone involving 18-dehydrogenase, also known as methyl oxidase defect type 2. The infant responded to therapy with fludrocortisone acetate, including catch-up growth in both length and weight. The disease is transmitted by an autosomal recessive gene.