A case report of right-sided heart failure secondary to JAK2-mutation Loeffler endocarditis.

Loeffler's endocarditis (LE) is the cardiac manifestation of hypereosinophilic syndrome. We present a case of LE in a 45-year-old female, resulting in diffuse endothelial fibrosis and severe right-sided heart failure. The patient was admitted with dyspnoea and oedema, with haematology revealing an absolute eosinophil count of 20.9 × 109. Imaging showed near-complete obliteration of the right ventricular apical and formation of thromboses. Endomyocardial biopsy indicated diffuse fibrous hyperplasia of the endocardium with fibrinous thrombi rich in eosinophils. Molecular and cytogenetic analyses of bone marrow cells showed no signs of FIP1L1-PDGFRA fusion, PDGFRB mutation, abnormal myeloid maturation, or a lymphoproliferative disorder. Flow cytometry indicated no clonality, ruling out chronic eosinophilic leukaemia. Gene mutation screening discovered a p.L583_A586delinesS mutation in the JAK2 gene. Following treatment with ruxolitinib, the patient's eosinophil levels normalized, but unfortunately, the damage to the heart was irreversible. The patient was hospitalized multiple times due to right heart failure and resistance to diuretics. After thorough discussions with the medical team, it was determined that a heart transplantation would be the most effective treatment. Following the surgery, the patient successfully navigated the postoperative critical period with the support of an intra-aortic balloon pump (IABP), continuous renal replacement therapy (CRRT), and ventilator-assisted ventilation but subsequently developed an acquired Intensive care unit-acquired weakness (ICU-AW) and a depressive state. Fortunately, the patient gradually recovered from these complications.