Fanconi syndrome in a patient with a variant of isovaleric acidemia.

Fanconi syndrome with proximal renal tubular acidosis is caused by a variety of anatomic, functional and metabolic disorders. We report a patient with a variant of isovaleric acidosis who developed proximal tubular acidosis. This patient was able to acidify the urine during metabolic acidosis, developed a hyperchloremic metabolic acidosis, and needed 24 mEq/kg/day of bicarbonate to maintain normal serum bicarbonate. She had a FE Bicarbonate of 12 +/- 4% during bicarbonate infusion. Isovaleric acidosis may be another toxic cause of proximal RTA.