What are the proposed morphologic criteria for diagnosis of sporadic inclusion body myositis (s-IBM)?

Updated: Jun 08, 2018
  • Author: Michael P Collins, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Proposed morphologic criteria for diagnosis of s-IBM (adapted from Griggs et al) [93] :

  • Inflammatory myopathy with endomysial mononuclear cell infiltration and invasion of non-necrotic MFs

  • Vacuolated MFs

  • Intracellular amyloid deposits, 15- to 21-nm nuclear and cytoplasmic tubulofilaments on electron microscopy, or positive SMI-31 staining.

Recent studies have shown that TDP-43, a nucleic acid binding protein normally located predominantly in myofiber nuclei, is found in IBM muscle sarcoplasm. TDP-43 immunoreactivity was noted to be more frequent than other biomarkers of IBM, with high sensitivity and specificity for the disease. [94]


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