Proximal Renal Tubular Acidosis (Fanconi Syndrome) Induced by Apremilast: A Case Report

Apremilast is a recently developed phosphodiesterase 4-inhibitory medication approved for use to treat psoriasis and psoriatic arthritis. We report a case of Fanconi syndrome and proximal renal tubular acidosis that was associated with this medication. Our patient was started on treatment with apremilast 2 weeks before his admission. On arrival, laboratory test results were significant for hypokalemia, hyperchloremic metabolic acidosis, low uric acid concentration, positive urine anion gap, and proteinuria, which resolved on discontinuation of the drug. Two months after the hospitalization, he was restarted on apremilast therapy; 17 days after resumption, the patient was admitted for similar laboratory values, which again improved when apremilast treatment was discontinued. After discharge, laboratory values remained normal without long-term electrolyte repletion. Proximal renal tubular acidosis (Fanconi syndrome) with quick correction of electrolyte concentrations on discontinuation of the drug was diagnosed. Our patient lacked evidence of other causes. Our patient fulfilled criteria associated with this disease and responded well off treatment with the offending agent. Literature review did not reveal prior cases associated with this medication.