A SURPRISING DISCOVERY - IDIOPATHIC HYPEREOSINOPHILIC SYNDROME

Introduction A 51-year old man with past medical history of allergic rhinitis was admitted to the hospital and treated for a right sided multi-lobar pneumonia. He presented with progressively worsening dry cough, malaise and diffuse (hip, knee, elbow, hands) joint pain. He had a history of multiple episodes of sinusitis and upper respiratory tract infections in the preceding six months requiring steroids and antibiotics with varying responses. A CBC revealed eosinophil count of > 9 eosinophils x 109/L. A BAL revealed over 90% eosinophils. He had a bone marrow biopsy showing moderate hypercellularity with marked eosinophilic hyperplasia and moderate megakaryocytic hyperplasia, though negative FISH results for PDGFRA, PDGFRB and FGFR1 rearrangements and normal cytogenetics. JAK2 and BCR-ABL were both negative. His clinical presentation along with the above findings was consistent with a diagnoses of idiopathic hypereosinophilic syndrome. He was started on prednisone in combination with hydroxyurea. He responded well to his current regimen. However, when his treatment was tapered he had a flare with now left sided pulmonary infiltrates and respiratory symptoms. With increase of treatment this again resolved. This case highlights the importance of investigating and initiating therapy for hypereosinophilia especially when end organ involvement is present. Furthermore, it shows eosinophilic pulmonary infiltrates can be unilateral despite this being a systemic process. It details the work-up that precludes diagnosis of this condition. Our case highlights the need for steroid sparing agents in long term management of idiopathic hypereosinophilic syndrome.