1. NP D.P.
Bx: 9/8/2017

7. CD3
CD68

8. MHC class I

9. A-SRP antibody(+) necrotizing myopathy
Normal immunohistochemical staining:
dystrophin; a-sarcoglycan; merosin; dysferlin; caveolin 3; a-dystroglycan; emerin.
Pathologic diagnosis:
Muscle, left thigh, biopsy:
Myopathy with necrotizing features, early chronic, active.
“a-SRP Ab found!!”
A-SRP antibody(+) necrotizing myopathy

10. Advances in the diagnosis & Treatment of Neuromuscular Disorders Pathology of inflammatory myopathy
Kurenai Tanji, M.D., Ph.D.
Neuromuscular Pathology Laboratory
Division of Neuropathology
Columbia University Medical Center

11. Inflammatory myopathy (IM): heterogeneous group of disorders
Infectious
Non-infectious
Immune-mediated (idiopathic) IM
macrophagic myofasciitis
granulomatous or eosinophilic myo-fasciitis
focal myositis (nodular myositis)
sarcoidosis
vasculitis
paraneoplastic involvement
graft vs. host disease
muscle involvement in collagen vascular disease
(e.g. MCTD, PR, RA, Sjogren, SLE, SS)
secondary inflammation in other myopathy (e.g. FSH, LGMDs)
Fix the content

12. Idiopathic IM Dermatomyositis (DM) Polymyositis (PM)
Inclusion body myositis (sIBM), sIBM-like syndrome
Immune-mediated necrotizing myopathies (IMNM)

13. Myositis- specific (related) Abs : ever-expanding list
Laboratory data
EMG
Myositis- specific (related) Abs : ever-expanding list
Abs a/w a-synthetase syndrome
a- Jo-1 >> a- PL-7, a- PL-12, a- EJ, a-OJ, a- KS, a-Zo
Abs a/w DM
a- Mi-2, a- p155/140, a- MJ (a-NXP2), a- MDA5, a- SUMO-1, a-TIFg (w/malignancy)
Abs a/w IMNM
a- SRP, a- HMGCR
Abs a/w MCTD, overlap syndrome
a- PM/Scl, a- U1RNP, a-Ku
Abs a/w sIBM
a-cN1A (specificity being questioned as of 2018)
Others : a- mito. Abs (myositis w/ or w/0 primary biliary cirrhosis); a-FHL1 (“severe inflam. myopath myopathies”);
a-AQP 4 (myelitis optica spectrum)
Others : muscle biopsy; ??? biomarker (? IP-10)

14. a + Degenerating/Necrotic fibers Regenerating fibers Myofiber atrophy
Tissue diagnosis
Degenerating/Necrotic fibers
Regenerating fibers
Myofiber atrophy
Evidence of inflammatory infiltration + a

16. a + Morphological hallmark of autoimmune myopathies
Degenerating/Necrotic fibers
Regenerating fibers
Myofiber atrophy
Evidence of inflammatory infiltration +
Distinctive histological features suggesting different pathophysiological mechanisms underlying each disease a

17. Dermatomyositis perifascicular pattern of involvement
For instance:
Dermatomyositis perifascicular pattern of involvement
perimysial > endomysial inflammation
Polymyositis CD8 (+) cytotoxic T-cell infiltration
perimysial < endomysial inflammation
IBM rimmed vacuoles
mitochondrial abnormality (secondary)

18. DM - Perifascicular pattern

20. DM, IMMUNE COMPLEXES (C5b-9) IN BLOOD VESSEL WALL