. 2014 Nov 7;178(3):405–415. doi: 10.1111/cei.12445

Table 1.

Idiopathic inflammatory myopathies

IM subtype	Muscle biopsy	Cellular infiltrate	Associated autoantibodies	References
Dermatomyositis	Perimysial and perivascular inflammation; perivascular atrophy; MAC deposition; MHC-I and II expression	CD4⁺ T cells; macrophages; B cells; plasma cells; BDCA-2 + plasmacytoid dendritic cells; CD8⁺ CD28^−/− and CD4⁺ CD28n^−/− T cells; mast cells; γ/Δ T cells	Anti-Mi 2	3,10,11,21–26
			Anti-TIF1y
			Anti-MDA5/anti-CADM-140
			Anti-NXP-2
			Anti-SAE
Polymyositis	Endomysial inflammation; MHC-I and II expression	CD8⁺ T cells; macrophages; myeloid dendritic cells; CD68⁺ macrophages; BDCA-1 + myeloid dendritic cells; CD8⁺ CD28^−/− and CD4⁺ CD28n^−/− T cells; mast cells; γ/Δ T cells	Anti-tRNA synthetases (e.g. anti-Jo)	3,10,11,21,25–27
Polymyositis	Endomysial inflammation; MHC-I and II expression		Anti-SRP	3,10,11,21,25–27
Inclusion body myositis	Endomysial inflammation; rimmed vacuoles; protein aggregation, inclusions; MHC-I and II expression	CD8⁺ T cells; macrophages; myeloid dendritic cells; CD68⁺ macrophages; BDCA-1 + myeloid dendritic cells	Anti-cN1A	3,21,25–27
Immune-mediated necrotizing myopathies	Endomysial and perimysial inflammation; MAC, MHC-I expression	CD68⁺ macrophages; few CD4⁺, CD8⁺ T cells, B cells	Anti-HMGCR	25,28–31
			Anti-SRP
			Anti-tRNA synthetases

Adapted and modified from Dimachkie [25]. MAC = membrane attack complex; MHC = major histocompatibility complex; BDCA = blood dendritic cell antigen; Tif = and transcriptional intermediary factor; MDA = melanoma differentiation-associated protein; NXP = nuclear matrix protein; CADM = clinically amyopathic dermatomyositis; SAE = small ubiquitin-like modifier activating enzyme; SRP = signal recognition particle; HMGCR = 3-hydroxymethyl glutaryl co-enzyme A reductase.