A rare condition that mimic myopathy: Late-onset glutaric acidaemia type II.

A 21-year-old woman visited the emergency department because of muscle weakness and hypoglycaemic coma. She had a 1-year history of exercise intolerance, myalgia and muscle weakness. Her body weight decreased from 65 to 40 kg. Physical examination at admission revealed neck and proximal limb muscle weakness (manual muscle testing 8 [MMT8] score, 26 points) accompanied by severe muscle atrophy. Her serum creatine kinase (CK) and lactate dehydrogenase (LDH) levels were 15514 U/L (reference interval [RI]: 40–200 U/L) and 1438 U/L (RI: 120–250 U/L), respectively, and serum myoglobin (Mb) level was 758.5 ng/mL. Abdominal ultrasonography showed severe hepatic steatosis and electromyography revealed features of myopathy. Magnetic resonance imaging (MRI) of her thigh muscles was normal. The patient was diagnosed with idiopathic inflammatory myositis (IIM), and she was treated with 60 mg/day methylprednisolone (MP) and coenzyme Q10 (10 mg, 3 times/day).