Abstract Introduction Hypereosinophilic syndrome (HES) is an uncommon disorder defined as peripheral eosinophilia greater than 1.5x109/L with organ damage. HES is classified as neoplastic, reactive, familial, or idiopathic. HES presentation is highly variable with dermatologic, pulmonary, gastrointestinal, cardiac and neurologic manifestations. Pulmonary involvement typically presents with asthma-like symptoms and computed tomography (CT) findings of patchy ground-glass opacities (GGO). Historically, treatment has centered around steroids although mepolizumab, an interleukin (IL)-5 monoclonal antibody, has been shown to reduce prednisone dose and eosinophilia.1 Given the rarity of this disease, radiologic response to mepolizumab is not well documented. Case Presentation An 83 year-old male with history of hypertension and prior mild eosinophilia (1.4x109/L) who was incidentally found to have eosinophilia 32x109/L. Work-up noted Strongyloides antibody and he was treated with ivermectin. One month later, he presented with a productive cough, dysphagia and night sweats. He had an eosinophilia 40.6x109/L and CT showed bronchial wall thickening, subpleural reticulations with bronchiolectasis and multistation lymphadenopathy up to 2.1x2.6cm. Bronchoscopy with endobronchial ultrasound with fine-needle aspiration found nonspecific eosinophil infiltration as was bone marrow biopsy and molecular genomic evaluation was negative for known HES mutations. Repeat infectious work-up noted downtrending Strongyloides antibody and no other overt infection, serum labs found severe eosinophilia 171x109/L and CT demonstrated of worsening bronchial wall thickening, increased patchy GGOs and consolidation, small bilateral pleural effusions and subsegmental PE. Following multidisciplinary discussion, prednisone 60mg was initiated. Eosinophilia dropped to 31x109/L but rebounded once prednisone weaned to 40mg. Mepolizumab was added to his treatment and subsequent eosinophil count dropped to 0.6x109/L with radiographic improvement (figure 1). Shortly after the second mepolizumab dose, he was hospitalized for Cytomegalovirus esophagitis and eosinophilia rebounded to 1.5-3.9x109/L range. Unfortunately, during this hospitalization he died from PEA arrest of unclear etiology. Discussion Pulmonary parenchymal involvement is noted in approximately 25% of HES cases. In patients who struggle to wean high-dose corticosteroids, the addition of mepolizumab may be beneficial at lowering steroid dose and eosinophilia. In our case, the patient had worsening CT pulmonary findings corresponding to progressive severe HES. Upon initiation of mepolizumab, there was improvement in eosinophilia which corresponded to radiologic improvement highlighting a potential outcome of interest for future studies. Citations: 1) Rothenberg ME, Klion AD, Roufosse FE, et al. Treatment of patients with the hypereosinophilic syndrome with mepolizumab. N Engl J Med. 2008;358(12):1215-1228. This abstract is funded by: none
Dunlop et al. (Fri,) studied this question.