What is the role of muscle biopsy in the workup of CNS lupus?

Updated: May 04, 2021
  • Author: Pradeep C Bollu, MD; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Muscle biopsy may provide the only reliable differentiation between inflammatory and medication-induced myopathy. Clinical evolution and medication history are most reliable, as creatine kinase is usually, but not always, elevated in inflammatory myopathy. Electromyography (EMG) is usually, but not always, abnormal in inflammatory myopathy, and both are usually normal in medication-induced myopathy. When other factors are ambiguous and empiric therapy is impractical, then muscle biopsy is appropriate.

Histologic evaluation most commonly reveals similar findings to those of nerve biopsies, emphasizing vascular and perivascular inflammation, similar to the muscle pathology in dermatomyositis. Less frequently, a pathology analogous to classic polymyositis is found, with inflammatory and other changes centered more on the muscle fibers, including frank necrosis, phagocytosis, and degeneration and regeneration of type I and II fibers.

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