Two pediatric oncologic cases of hypereosinophilic syndrome and review of the literature

BACKGROUND: Persistent peripheral blood hypereosinophilia may cause tissue damage, leading to hypereosinophilic syndrome (HES) with end‐organ dysfunction. Here we discuss two unique pediatric cases of primary hypereosinophilic syndrome with oncologic etiologies to highlight the importance of early recognition, workup and treatment of HES. CASE 1: A previously healthy 7‐year‐old male presented with acute myocardial infarction and transient ischemic attack and found to have significant hyperleukocytosis with a total white blood count of 131 000 and hypereosinophilia with an absolute eosinophil count of 99 560. He was ultimately diagnosed with precursor B‐cell acute lymphoblastic leukemia with immunoglobulin heavy chain gene rearrangement. He completed standard treatment without significant complications and remains in remission at about 2 years off therapy. He is in overall good health and has normal cardiac function. CASE 2: A 13‐year‐old female was referred for iron deficiency and reported a history of severe anxiety, shortness of breath and anorexia. She had experienced fatigue and dizziness associated with frequent panic attacks and shortness of breath with strenuous activity since the age of five. Serial laboratory investigations revealed persistent hypereosinophilia (AEC 4000‐6000/μl). Additional workup revealed elevated vitamin B12 (>2000 pg/ml; normal range: 243–894) and tryptase (16.4 ng/ml; normal range: ≤10.9). The FIP1L1‐PDGFRA gene fusion was detected by fluorescence in situ hybridization (FISH) on peripheral blood, diagnostic for myeloid/lymphoid neoplasm with eosinophilia. Evaluation for end‐organ damage associated with persistent hypereosinophilia included an echocardiogram which revealed severe restrictive cardiomyopathy with pulmonary hypertension. Monotherapy with imatinib was initiated, after which she achieved a rapid hematologic response and remains in molecular remission, though she continues to have persistent asymptomatic severe pulmonary hypertension in the setting of severe diastolic dysfunction. CONCLUSION: Persistent hyperosinophilia can be a silent cause of significant and often irreversible tissue damage and should therefore always prompt workup for both primary and secondary causes.