Anorexia nervosa, laxative abuse, hypopotassemia and distal renal tubular acidosis

A case of anorexia nervosa in a 28-year-old woman with laxative abuse, hypopotassemia and severe metabolic acidosis, is described. The diagnosis of classical renal tubular acidosis, Type I, was confirmed by our inability to decrease urinary pH beyond 5.5 and to increase ammonia excretion during an ammonium chloride loading test. A bicarbonate loading test and normal plasma aldosterone with high renin activity excluded proximal renal tubular acidosis, hyporeninemic-hypoaldosteronemic renal tubular acidosis and Bartter's syndrome. The inability to increase ammonium excretion during severe metabolic acidosis following ammonium chloride loading did not favor the possibility of a transient physiological adaptation of ammoniagenesis at the tubular cell level, related to potassium depletion. Although mental disorder, laxative abuse, abstinence from food intake and severe potassium depletion intermingled in a vicious cycle, we assume that one of the following possibilities may explain the clinical presentation in our patient: either two separated and unrelated disorders, or laxative abuse as the cause of renal tubular acidification impairment.