Caseous calcification of the mitral annulus-associated calcified amorphous tumour with chronic inflammatory cardiomyopathy: a case report.

Background: Calcified amorphous tumour (CAT) is a rare lesion that forms at various sites of the heart, including the mitral annulus. Since it is a systemic embolic source, it often requires resection. In contrast, caseous calcification of the mitral annulus (CCMA) usually receives conservative follow-up; however, it is sometimes resected to prevent embolism. Herein, we present a rare case of CCMA-associated CAT with chronic inflammatory cardiomyopathy and comprehensively consider the aetiology of CCMA-associated CAT. Case summary: A 52-year-old man with end-stage renal failure requiring haemodialysis underwent annual follow-up echocardiography for aortic valvular dysfunction. Echocardiography revealed a well-defined 22 × 17-mm circular mass on the annulus of the posterior mitral leaflet that had not been detected 2 years previously. Based on imaging characteristics, the mass was suspected to be a CCMA. It had rapidly enlarged and posed a potential risk for embolism; therefore, it was resected concurrently with aortic valve replacement. Although CCMA was suspected based on the intraoperative findings, the histopathological diagnosis was a CAT. Upon histological analysis of the left ventricular myocardial specimen and excised aortic valve, chronic inflammatory cell infiltration was observed; therefore, chronic inflammatory cardiomyopathy was diagnosed. Discussion: In this case, the timing of decreased left ventricular systolic function and the arising mass coincided, suggesting that chronic inflammation and immunopathological reactions may have influenced the development of CAT from CCMA. Therefore, the rapid progression of CCMA in the development of CAT should especially be considered in patients with inflammatory cardiac comorbidities.