October 8, 2021
Hematoxylin and eosin; 200x and 400x original magnifications
This 60-year-old patient presented with fevers and bilateral leg myalgias of one month’s duration. Laboratory studies demonstrate elevated ESR (120) and normal CPK. On physical examination, the patient had pain upon palpation of both calf muscles. Muscle biopsy was performed.
Given the clinical history and features seen in the image, what additional laboratory test results would be best to request?
B. Stool ova and parasites
C. C-reactive protein
The image shows the circumferential presence of mononuclear histiocytes within the wall of a small artery (i.e. non-caseating granulomatous inflammation). No multinucleate histiocytes (so-called “giant cells”) are seen. Sparse surrounding chronic inflammation comprised of mature lymphocytes and scattered eosinophils is present. The more central ring of lace-like brightly eosinophilic material represents “fibrinoid necrosis”: a zone of endothelial cell death related to antigen-antibody complex deposition along the inner aspect of the blood vessel wall admixed with fibrin.
The morphologic changes are those of a “granulomatous vasculitis.” Serologic testing for anti-neutrophil-cytoplasmic antibodies (ANCA) is warranted to further evaluate for the presence of an ANCA-Associated Vasculitis (AAV).
Immunoassay for PR3-ANCA and MPO-ANCA is currently the recommended International standard.
AAV encompass Granulomatosis with Polyangiitis (GPA: previously Wegener’s Granulomatos), Microscopic Polyangiitis (MPA), and Eosinophilic Granulomatosis with Polyangiitis (EGPA: previously Churg-Strauss Syndrome)
Of note: although eosinophils are commonly seen in the setting of EGPA, they may be seen in the setting of other vasculitides, and are therefore not specific to EGPA.
Yates M, Watts R. ANCA-associated vasculitis. Clin Med (Lond). 2017;17(1):60-64. doi:10.7861/clinmedicine.17-1-60
Kallenberg CG. Key advances in the clinical approach to ANCA-associated vasculitis. Nat Rev Rheumatol. 2014 Aug;10(8):484-93. doi: 10.1038/nrrheum.2014.104. Epub 2014 Jul 1. PMID: 24980139.
Bossuyt X, Cohen Tervaert JW, Arimura Y, Blockmans D, Flores-Suárez LF, Guillevin L, Hellmich B, Jayne D, Jennette JC, Kallenberg CGM, Moiseev S, Novikov P, Radice A, Savige JA, Sinico RA, Specks U, van Paassen P, Zhao MH, Rasmussen N, Damoiseaux J, Csernok E. Position paper: Revised 2017 international consensus on testing of ANCAs in granulomatosis with polyangiitis and microscopic polyangiitis. Nat Rev Rheumatol. 2017 Nov;13(11):683-692. doi: 10.1038/nrrheum.2017.140. Epub 2017 Sep 14. PMID: 28905856.
Bajema IM, Bruijn JA. What stuff is this! A historical perspective on fibrinoid necrosis. J Pathol. 2000 Jul;191(3):235-8. doi: 10.1002/(SICI)1096-9896(0000)9999:99993.0.CO;2-I. PMID: 10878543. Bajema IM, Bruijn JA.
Khoury P, Grayson PC, Klion AD. Eosinophils in vasculitis: characteristics and roles in pathogenesis. Nat Rev Rheumatol. 2014 Aug;10(8):474-83. doi: 10.1038/nrrheum.2014.98. Epub 2014 Jul 8. PMID: 25003763; PMCID: PMC4849122.