Eosinophilic myocarditis in dilated cardiomyopathy: a case report.

BACKGROUND: Eosinophilic myocarditis (EM) is a rare cardiac condition that is often difficult to diagnose. Although endocardial myocardial biopsy is considered the gold standard for diagnosis, sampling errors can lead to false-negative results. This case report discusses the diagnosis and treatment of dilated cardiomyopathy in a patient with EM.

CASE PRESENTATION: In this article, we report a case of a 32-year-old female patient diagnosed with dilated cardiomyopathy. EM was strongly suspected based on a progressive increase in eosinophil count, the absence of known allergens or common etiological factors, elevated eosinophil levels in alveolar lavage fluid, and a diagnosis of eosinophilic pneumonia. However, endocardial myocardial biopsy results failed to show definite evidence of myocarditis. Despite the implementation of various therapeutic interventions including pharmacological treatments, electrical defibrillation, endotracheal intubation, and ventilator-assisted breathing, the patient's condition showed minimal improvement. Subsequent initiation of extracorporeal membrane oxygenation and intra-aortic balloon pump support also failed to achieve the anticipated recovery. The patient subsequently underwent heart transplantation, and cardiac tissue samples were sent for pathology examination. The diagnostic report revealed a large number of eosinophils, confirming the diagnosis of EM. After heart transplantation, the patient's vital signs gradually stabilized, and she was discharged in good condition.

CONCLUSIONS: Endocardial myocardial biopsy plays an important role in diagnosing EM but may yield false-negative results. In this case, heart transplantation provided critical diagnostic information, with the pathology report confirming the presence of eosinophils and supporting the diagnosis of EM.