A Rare Case of Hypereosinophilic Syndrome-Induced Shower Thrombus Responsive to Nilotinib

Hypereosinophilic syndrome (HES) is a rare clinical disease that affects 0.036/100,000 patients, with a minority of patients having associated genetic markers which can encompass PDGFRA/B or FGFR1 mutations. The prognosis is dependent on the timing of diagnosis and early treatment, with a mortality rate ranging from 48% to 75% if there is a delayed diagnosis. Eosinophilic myocarditis is characterized by invasion of the myocardium with eosinophils. Myeloid neoplasms are a rare, but known cause of HES induced myocarditis. Signs and symptoms can range from being asymptomatic to retrosternal pain, arrhythmias, and even sudden death. HES myocarditis is a diagnosis of exclusion that is made via endomyocardial biopsy. Peripheral eosinophilia is the only specific sign to suggest eosinophilic myocarditis with traditional biomarkers, electrocardiogram, and echocardiogram. Treatment modalities include systemic corticosteroids and symptomatic management. Complications from HES myocarditis may include embolic events, eosinophilic vegetations, and dysrhythmias, or conduction disturbances. We present a case of a 62-year-old male who initially presented with epigastric pain, and then suffered a myocardial infarction. After testing, the probable diagnosis of eosinophilic myocarditis was made. His clinical course was complicated by the development of shower thrombus associated with acute encephalopathy. Although HES has classically been treated with imatinib, in this case, an alternative biologic agent was used, resulting in a good prognosis and ultimate patient survival. This case details the importance of early clinical suspicion, diagnosing the condition, and early initiation of treatment to prevent worsening clinical status.