[Infectious myopathies and sarcoid myopathy]

The differential diagnosis of inflammatory myopathies is multifarious and includes not only neurological, metabolic and toxic causes but also infectious myopathies and sarcoid myopathy. This review article focuses on the latter two entities. Infectious myopathies are rare and can be classified into bacterial, viral, parasitic and fungal forms. The main symptoms include muscle pain, swelling and weakness. Bacterial myopathies are usually secondary in origin (hematogenous spread, trauma, immunosuppression). The most frequent form is pyomyositis, predominantly caused by Staphylococcus aureus, presenting with fever, pain and abscess formation. Fulminant courses such as necrotizing myositis require immediate surgical intervention. In contrast, viral myopathies are the most frequent infectious cause and typically present with diffuse, self-limiting muscle involvement. Typical pathogens include influenza viruses, enteroviruses and herpesviruses. Complications can range up to rhabdomyolysis. Parasitic myopathies are often associated with eosinophilia and granulomatous inflammation (e.g. Toxoplasma, Trichinella, Taenia). Fungal myopathies predominantly affect immunocompromised patients and present with abscess formation. Sarcoid myopathy (SaM) is a rare manifestation of sarcoidosis (approximately 1-2%). It presents with different clinical phenotypes (nodular, smoldering, myopathic and combined) and usually occurs in the context of multisystem disease. Creatine kinase levels are often normal. Magnetic resonance imaging (MRI) is diagnostically helpful, while definitive diagnosis requires histological confirmation of non-caseating granulomas. Glucocorticoids and methotrexate are the mainstay of treatment.