Unusual diagnosis in a Lebanese child with persistent hyper eosinophilia: a case report.

Introduction and Importance: The differential diagnoses of hypereosinophilia (HE) are diverse and may include parasitic infections, allergic or atopic diseases, and malignancies. The list of differentials for hypereosinophilia is diverse and a comprehensive workup can often be expensive. However, it is essential to identify the underlying cause and treat it rather than treating eosinophilia itself. Case presentation: A 5-year-old male patient was referred to a pediatric hemato-oncologist for concerns of persistent hypereosinophilia, and the absolute eosinophil count (AEC) was greater than 1000 in three recent complete blood count with differentials. The child presented complaining of alternating waxing and waning right and left ankle and knee redness, hotness, pain, and decreased range of motion that occurred every 2 weeks, with associated lack of appetite, fatigue, constipation, and fever reaching 39°C. Clinical discussion: Malignant eosinophilic infiltration of the bone marrow versus a parasitic infection was on top of the differential diagnoses. Presentations of HE suggesting organ system involvement include fever, weight loss, wheezing, cough, dysphagia, vomiting, lack of appetite, diarrhea, arthralgia, and myalgia. Conclusion: Identifying the etiology of persistent hypereosinophilia can be challenging in the pediatric population and can have diverse presentations. The primary focus during initial HE assessment is on evaluating the severity of symptoms and potential organ damage. Major life-threatening diagnoses as malignancies and immune deficiencies must be ruled out first when the AEC is persistently elevated. Parasitic infections should be investigated according to the geographic endemicity.