Late-onset multiple acyl-CoA dehydrogenase deficiency mimicking myositis in an elderly patient: a case report

BACKGROUND: Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare and treatable inherited lipid storage myopathy. Here, we report an elderly patient with MADD mimicking myositis. CASE PRESENTATION: An 80-year-old woman had progressive weakness in her limbs, exercise intolerance, and no muscle pain for 3 months. The patient’s serum creatine kinase level was slightly elevated. The initial diagnosis was myositis. However, muscle biopsy showed many cytoplasmic vacuoles stained with oil red O, indicating the presence of lipid storage myopathy. The plasma acylcarnitine profile showed increased medium-chain and long-chain acylcarnitine species, consistent with the diagnosis of MADD. Riboflavin treatment dramatically improved muscle weakness. CONCLUSIONS: MADD should be considered when evaluating elderly patients with subacute muscle weakness. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12883-020-02010-w.