Hyperkalemia and Renal Tubular Acidosis Due to Renal Amyloidosis

A 46-year-old white man presented with renal amyloidosis, secondary to chronic osteomyelitis of leg and associated with renal tubular acidosis and severely impaired renal potassium excretion. Inulin clearance was 25 ml/min; creatinine clearance, 29 ml/min; and potassium clearance, 3.5 ml/min. Hyperkalemia was common despite a low potassium intake and correction of acidosis. Total body potassium was high at 55 mEq/kg body weight. There was no evidence of adrenal insufficiency, and potassium clearance was unaffected by hyperkalemia, increased sodium intake, sodium bicarbonate loading, increased urinary flow rates, or by a thiazide diuretic; administration of a very large dose of mineralocorticoid was associated with a slight increase in potassium clearance. There was no evidence of a proximal tubule defect, and the patient could concentrate urine above the osmolality of plasma.

The patient was followed for 18 months, and over that period no change in glomerular or tubular function was detected. In addition to typical deposition of amyloid in the glomeruli, renal biopsy showed marked peritubular amyloid in the cortex and medulla. It is postulated that this interfered with sodium-potassium and sodium-hydrion exchange in the distal nephron, resulting in hyperkalemic renal tubular acidosis.