2020 Volume 84 Issue 7 Pages 1194-
A 50-year-old Japanese man was admitted to because of a digital ulcer and interstitial pneumonia. He was referred to a rheumatologist because echocardiography had revealed diffuse hypokinesis of the left ventricle with an ejection fraction (LVEF) of 38% without LV dilatation and hypertrophy. His laboratory data showed white blood cells 4,500/mm3, high-sensitivity troponin T 0.023 ng/mL, C-reactive protein, 0.07 mg/dL, and N terminal-pro-B-type natriuretic peptide (NT-proBNP), 582 pg/mL. ECG findings were unremarkable. Because coronary angiography showed 75% stenosis of the left circumflex branch, a right ventricular endomyocardial biopsy was performed. Microscopically, replacement fibrosis and mononuclear cell infiltration with myocyte damage were seen (Figure A,B). There were more macrophages, followed by T cells (more CD8-positive cells than CD4-positive cells) and few B cells (Figure C–F). Moreover, macrophages were mainly M2 (Figure G,H), and the nuclei of some interstitial cells and myocytes were positive for phospho-Smad2 (Figure I), which may be related to cardiac remodeling.
Endomyocardial biopsy shows fibrosis (A, Azan) and cell infiltration with myocyte damage (arrows) (B, H&E). Immunohistochemical staining shows more CD68-positive cells (C, arrows) followed by T cells (more CD8-positive cells (D, arrows) than CD4-positive cells (E, arrows)) and few L26-positive B cells (F). Macrophages are mainly M2 (G, CD163; arrows), not M1 (H, CD11c). Some interstitial cells (arrows) and myocytes (arrowheads) were positive for phospho-Smad2 (I).
He was diagnosed with clinically amyopathic dermatomyositis (CADM), a unique subset of polymyositis-dermatomyositis with typical skin manifestations with little or no evidence of musculoskeletal involvement, by skin and muscle biopsy, and laboratory data including positive for anti-Melanoma differentiation-associated gene 5. About 3 months after starting treatment with prednisolone and tacrolimus in addition to enalapril, NT-proBNP decreased to 221pg/mL, and echocardiography showed improvement of the LVEF (54%). Thus, chronic myocarditis may be related to CADM.
K.M. is a member of Circulation Journal’ Editorial Team. The other authors declare no conflicts of interest.
