Prominent medial hypertrophy of renal arterioles in an infant with hyporeninemic hypoaldosteronism

We describe an 11-month-old boy who presented clinically with hyperkalemic renal tubular acidosis due to hyporeninemic hypoaldosteronism. Persistent h yperchloremic acidosis and mild azotemia were present. All abnormal laborat ory values were corrected by the administration of fludrocortisone. Renal b iopsy showed prominent medial hypertrophy of renal arterioles and interstit ial fibrosis, which closely resemble those of the gene-targeted mice with d isruption of the renin angiotensin system. This is the first case report ra ising the possibility that a defective renin angiotensin system in infancy may lead to tubulointerstitial damage with medial hypertrophy of intrarenal arterioles.