Fig. 4

Granulomatous myositis overlapping with IBM. Pathomorphological characteristics of granulomatous myositis overlapping with IBM as seen on muscle biopsy. (a) Granulomatous inflammatory infiltrates with sparse giant cells and intermingled single myofibers. Gömori trichrome staining (× 200). (b) Severe fiber size variation with hypotrophic and hypertrophic fibers as well as multiple rimmed vacuoles. Gömori trichrome staining (× 400). (c) Presence of multiple COX-negative and SDH-positive myofibers. COX-SDH staining (× 200). (d) Myofibers display sarcolemmal (and sarcoplasmic) positivity for MHC class I. MHC class I staining (× 200). (e) Myofibers display sarcolemmal (and sarcoplasmic) positivity for MHC class II. MHC class II staining (× 200). (f) Coarse p62⁺ autophagic material mostly localized in vacuoles and subsarcolemmaly with some fibers showing more fine granular autophagic material (× 400). COX  cytochrome oxidase immunohistochemistry; IBM  inclusion body myositis; MHC  major histocompatibility complex; SDH  succinate dehydrogenase