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Journal Review: Granulomatous myopathy: Sarcoidosis and beyond
Journal Review: Granulomatous myopathy: Sarcoidosis and beyond

Non-necrotizing granulomatous inflammation is a rare but easily recognized histo-pathological finding in skeletal muscle biopsy. A limited number of diseases are known to be associated with non-necrotizing granulomatous myopathy. Once identi-fied, a careful evaluation for evidence of extramuscular granulomatosis and other signs suggestive of sarcoidosis is warranted as about half of the patients have sarcoid myopathy. In addition, the presence of granulomatous myopathy should trigger a search for clinical and pathological clues of inclusion body myositis (IBM), which accounts for most of the remaining patients and can coexist with sarcoidosis. Recog-nizing the features of IBM in patients with granulomatous myopathy can potentially spare the patients from unnecessary exposure to immunosuppressive therapies. In patients whose granulomatous myopathy remain unexplained, further investigations should aim at identifying myasthenia gravis and other autoimmune disorders, espe-cially those known to cause granulomatous inflammation in other organs. Laboratory investigations should include acetylcholine receptor, antimitochondrial, antineutro-phil cytoplasmic, thyroglobulin, and thyroid peroxidase autoantibodies. In the appropriate clinical context, exposure to immune checkpoint inhibitors and chronic graft-vs-host disease can be causes of granulomatous myopathy. In cases of unexplained granulomatous myopathy, natural killer/T-cell lymphoma should be con-sidered and careful histopathological examination for atypical cells and appropriate immunostaining is crucial. Identifying the etiology of granulomatous myopathy in each patient can guide appropriate treatment.

1)Understand and recognize the clinical features of non-necrotizing granulomatous myopathies;
2) Be able to recognize the histopathological features of non- necrotizing granulomatous myopathies;
3) Be able to develop a focused and logical diagnostic evaluation of patients with suspected granulomatous myopathy.  

The AANEM is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

The AANEM designates this enduring material for a maximum of 1 AMA PRA Category 1 Credits TM.  Physicians should claim only the credit commensurate with the extent of their participation in the activity. Credit expires 2/1/2026.

The authors have no conflicts of interest. 

Pitcha Chompoopong, MD; Teerin Liewluck, MD
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