Chronic myocarditis with a long clinical course: Report of an autopsy case of probable autoimmune myocarditis.

The patient was a 54-year-old woman, who died of chronic cardiac insufficiency after a clinical course of 2 years and 4 months. She had complained of myalgia, muscle weakness, and blepharoptosis before the onset of cardiac symptoms, but there was no evidence of myasthenia gravis or collagen-vascular diseases. At autopsy, the heart (280 g) showed marked dilatation of the four chambers and thinning of the ventricular walls. Diffuse and intense lymphocytic infiltration and extensive fibrosis were noted, with the latter being accentuated in the subendocardial and subepicardial zones. Small foci of myocardial necrosis were scattered and a small number of multinucleated giant cells were found, but epithelioid cell granulomas, Aschoff's nodules, and viral inclusion bodies were not observed. Some cardiomyocytes showed the aberrant expression of the HLA-DR antigen. No viral genomes were detected in myocardial tissue using a multivirus real-time polymerase chain reaction. The protracted clinical course, presence of active inflammatory changes at autopsy, expression of the HLA-DR antigen on cardiomyocytes, and absence of viral genomes in myocardial tissue suggest that autoimmune mechanisms played an important role in the pathogenesis and persistence of myocarditis in this patient.
(© 2017 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.)