myopathies

Myopathy is a broad term for diseases that primarily affect skeletal muscle, causing weakness and reduced endurance. These conditions can be inherited or acquired and may involve defects in muscle fibers, energy metabolism, inflammation, or other cellular processes. Myopathies are distinguished from nerve and neuromuscular junction disorders by primary muscle pathology on examination, biopsy, or genetic testing.

Classification and examples vary by approach. Broadly, myopathies are organized as hereditary (genetic) or acquired. Hereditary myopathies include muscular dystrophies, congenital myopathies, and metabolic myopathies. Acquired myopathies include inflammatory (such as polymyositis and dermatomyositis), endocrine and metabolic myopathies (for example, Cushing’s or hyperthyroid myopathy, Pompe disease), and drug- or toxin-induced forms.

Clinical presentation is usually symmetric proximal muscle weakness, often with difficulty rising from a chair, climbing stairs, or lifting objects. Fatigability, scoliosis, and neck or shoulder girdle weakness may occur. Some patients develop cramps, myalgias, or respiratory muscle involvement. Serum creatine kinase is often elevated, particularly in inflammatory and metabolic myopathies. Diagnosis integrates history, physical examination, blood tests, electromyography, MRI of muscles, muscle biopsy, and genetic testing when appropriate.

Management is condition-specific and multidisciplinary. General measures include physical and occupational therapy, regular aerobic and resistance exercise adapted to ability, and nutritional support. Treatable forms include inflammatory myopathies (immunotherapy), Pompe disease (enzyme replacement therapy), and other metabolic disorders. Medication is avoided in drug-induced forms, and management targets underlying causes, complications, and quality of life. Ongoing research explores gene therapy and targeted treatments. Prognosis varies widely by type and severity.