Summary

• Heterogeneous group of muscular disorders characterised by progressive muscle weakness.
• Presentation is sub-acute or chronic and rarely acute.
• May be associated with dysphagia, fatigue, difficulties with breathing, and skin lesions.
• Diagnosis is confirmed by elevated serum muscle-derived enzymes, typical electromyography (EMG) findings, and inflammation on muscle biopsy.
• Corticosteroids are first-line therapy. Intravenous immunoglobulin, methotrexate, and azathioprine are used as second-line therapy. Third-line therapies include cyclophosphamide, mycophenolate, ciclosporin, and tacrolimus.