Rapid progression of constrictive pericarditis due to primary malignant pericardial mesothelioma: A case report.

Primary malignant pericardial mesothelioma (PMPM) is a rare malignancy, accounting for 0.7% of all mesotheliomas and has non-specific clinical features such as dyspnea and chest pain. A 66-year-old man visited a referring physician with a chief complaint of worsening dyspnea on exertion. Imaging revealed irregular pericardial thickening and hemorrhagic effusion. Despite initial empirical management with antibiotics and steroids under the diagnosis of constrictive pericarditis (CP) of unknown etiology, his condition deteriorated rapidly; he was transferred to our hospital for advanced therapy. However, on the night of referral, the patient experienced cardiac arrest due to atrial arrhythmia and required percutaneous cardiopulmonary circulatory support. Based on the rapid progression of clinical features and imaging findings, we considered that his CP was caused by a malignancy, in which case, his condition did not warrant radical pericardiectomy. Intraoperative frozen section analysis from an open biopsy via a small subxiphoid incision confirmed malignancy, and the patient was transitioned to palliative care. The patient died eight days after admission. Histopathological examination revealed sarcomatoid PMPM. This case highlights the importance of considering PMPM in rapidly progressive CP, emphasizing the diagnostic challenge and the need for early recognition especially when imaging reveals irregular pericardial thickening and hemorrhagic effusion. Learning objective: Primary malignant pericardial mesothelioma can closely mimic constrictive pericarditis, leading to delays in diagnosis and management. This case underscores the necessity of early suspicion of malignancy in patients with rapidly progressive constrictive pericarditis presenting with hemorrhagic pericardial effusion and irregular pericardial thickening.