Muscle Weakness & Pain

General Approach

• Review medications for agents that may cause muscle weakness, e.g.

  • Antithyroid agents (methimazole, propylthiouracil)

  • Chemotherapeutic agents

  • Corticosteroids

  • Statins

• Labs

  • Obtain CBC, CMP, TSH, creatinine kinase, ESR, CRP, antinuclear antibody

  • Consider obtaining

    • STI testing: HIV fourth generation (ELISA), rapid plasma reagin (RPR)

    • Lyme antibodies (Borrelia Antibodies, IgM/IgG)

    • Additional rheumatologic testing only if ANA is positive

• No identifiable etiology s/p initial testing: Consider electromyography, muscle biopsy

Differential

• Emergent: Ischemic stroke

• Endocrine

  • Hypothyroidism

  • Hyperthyroidism

• Neurologic

  • Demyelinating disorders

    • Multiple findings: Multiple sclerosis

    • Ascending: Guillain-Barré

  • Anterior horn cells: Amyotrophic lateral sclerosis

  • Neuromuscular junction

    • Myasthenia gravis

    • Lambert-Eaton syndrome

    • Pediatric: Botulism

• Muscle fibers

  • Statin-induced myopathy

  • Polymyalgia rheumatica

  • Polymyositis and dermatomyositis

  • Pediatric: Duchenne muscular dystrophy

• Neuropsychiatric

  • Fibromyalgia

  • Depression

  • Conversion disorder