Fanconi Syndrome Associated with Valporic Acid: A Case Report

Dear Editor, Fanconi syndrome is the most common cause of proximal renal tubular acidosis (RTA) in children and is characterized by hypophosphatemia due to phos-phaturia, renal glucosuria (glucosuria with a normal plasma glucose concentration), aminoaciduria, and normal anion gap metabolic acidosis. Muscle weakness is one of the Fanconi syndrome manifestations. Valporic acid (VPA) is an anti-epileptic drug widely used to treat partial and generalized seizures especially in children. Fanconi syndrome is a rare side effect in children during long-term VPA treatment. 3,4 Herein, we reported a 14-year-old Iranian boy with progressive muscle weakness. He was diagnosed as a case of Fanconi syndrome secondary to VPA administration and showed dramatic response to treatment by carnitine supplement. The 14-year-old Iranian boy was referred to Mofid Children's Hospital because of progressive muscle weakness. He was treated with VPA for 2 years due to his seizures attacks. With the exception of epilepsy , he was a healthy and active boy with normal development and no relevant findings in his past medical history. Almost one year after he was started on VPA, he developed progressive muscle weakness with myalgia and gradually he became unable to walk. On physical examination, muscle atrophy was detected and his proximal and distal muscle strength in both upper and lower limbs decreased. His Laboratory findings were as follows: Metabolic acidosis (VBG=pH 7.14, PCo 2 = 41.9 mmHg, serum bicarbonate=12.3 mmol/L), hypophos-phatemia (p=3.2 mg/dL), hypokalemia (k=2.47 mEq/dL) with normal calcium (9.2 mg/dL). The patient also had proteinuria (1+), glucosuria (1+) and his urine pH was 6, which were compatible with Fanconi syndrome. Blood urine nitrogen and creatinine levels were 3 mg/dL and 0.9 mg/dL respectively. His parathormone hormone level was normal. Random sample of urine showed urine phosphorous of 131.4 mg/dL, urine calci-um=186 mg/dL, and urine cratinine=29 mg/dL. Kidney ultrasound revealed hyperechogenicity in both kidneys and his muscle biopsy was highly compatible with mitochondriopathies or carnitine deficiency. Because VPA appears to be the first suspicion for renal involvement, it stopped and carnitine was administered. Within 3 months, the muscle weakness improved and his kidney function recovered. People treated with VPA experienced some side effects; however, it is widely used as an effective anti-epileptic drug. One of the important side effects of VPA is acquired type of Fanconi syndrome. A PubMed-based review of the literature revealed that Fanconi syndrome was a rare side effect in children during VPA treatment. However, the detailed …