Methylphenidate-associated myopathy

Abstract

Methods We describe a case of a 13 yo girl diagnosed with ADHD since early childhood, in MP use for the past 3 years. She complained about a mild discomfort of proximal muscles of the lower limbs and cramps for the previous 3 months. Routine exams revealed increased aminotransferases levels (AST 192 UI/L; ALT 222 UI/L), suggesting hepatotoxicity. New laboratory tests were ordered, showing a CPK level of 18300 UI/L, AST 393 and ALT 330. The MP use became intermittent while the investigation was performed. Two weeks later, AST was 80 and ALT 166. A thorough investigation showed negative viral serology (HAV, HBV, HCV, HIV, CMV and EBV); negative autoantibodies (FAN, anti-LKM, anti-smooth muscle, anti-TPO and anti-tireoglobulin); normal hemogram; negative inflammatory markers (ESR and PCR) and a normal lower limbs MRI. An ECG revealed an altered antero-septal repolarization and echocardiogram was normal. Twenty days after, a new lab evaluation revealed a decreasing level of CPK (9670). One month after the complete withdrawal of the MP, the myalgia and cramps were no more present and CPK levels decreased to 3160mg/dl.