{Reference Type}: Case Reports {Title}: A case report on multiple acyl-CoA dehydrogenase deficiency with severe myopathy and osteoporosis. {Author}: Li M;Lin ZH;Chen YC;Lin P;Xie YX;Wei JC; {Journal}: Int J Rheum Dis {Volume}: 27 {Issue}: 1 {Year}: 2024 Jan 22 {Factor}: 2.558 {DOI}: 10.1111/1756-185X.14906 {Abstract}: A 35-year-old male patient presented fluctuating bilateral lower extremity weakness for 3 years. Physical examination showed grade 4 proximal muscle weakness in both lower extremities and grade 5 distal muscle weakness. Laboratory data revealed elevated creatine kinase, triglycerides, and cholesterol. Muscle pathology showed deposition of lipid droplet under the sarcolemma. Bone densitometry indicated severe osteoporosis. Next-generation sequencing revealed a pathogenic mutation in the ETFDH gene. The patient was diagnosed with late-onset multiple acyl-CoA dehydrogenase deficiency. After riboflavin treatment, symptoms of the patient were relieved, physical endurance was restored, and bone mineral density was improved.