Eosinophilic Granulomatosis With Polyangiitis Misdiagnosed as Hyper-Eosinophilic Syndrome: A Case Report

Abstract

Eosinophilic disorders include a spectrum of conditions characterized by elevated eosinophil levels in peripheral blood and/or tissues, presenting with diverse systemic manifestations. Hyper-eosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA) represent two distinct entities within this spectrum, each with unique clinical features and therapeutic approaches. We report the case of a 42-year-old Afghan male with a history of smoking, who presented with progressive weakness and paresthesia in all four limbs, along with constitutional symptoms including low-grade fever, night sweats, unintentional weight loss and asthma. Initial laboratory investigations revealed persistent eosinophilia, leading to a presumptive diagnosis of idiopathic HES. Despite treatment with imatinib, his symptoms worsened. Neurological examination showed bilateral foot drop, generalized muscle wasting, and sensory deficits, consistent with peripheral neuropathy. A maculopapular rash and late-onset sinusitis further complicated the clinical picture. Bone marrow biopsy revealed eosinophilic hyperplasia without atypical cells, and fluorescence in situ hybridization (FISH) testing for the Fip1-like 1 and platelet-derived growth factor receptor alpha (FIP1L1::PDGFRA) rearrangement was negative, excluding a detectable FIP1L1::PDGFRA-associated clonal eosinophilic disorder. A comprehensive evaluation for secondary causes of eosinophilia, including parasitic infections, was negative, and cardiac assessment showed no evidence of cardiac involvement. A positive antineutrophil cytoplasmic antibody (ANCA) test and nerve conduction studies (NCS) ultimately led to a revised diagnosis of EGPA. The patient was treated with intravenous methylprednisolone followed by cyclophosphamide, in accordance with the 2021 American College of Rheumatology and European Alliance of Associations for Rheumatology (ACR/EULAR) vasculitis guidelines. This regimen resulted in marked clinical improvement within 1 month, with progressive recovery of muscle strength and improvement in the rash and neuropathic symptoms. Over 6 months of follow-up, the patient demonstrated sustained improvement, with normalization of eosinophil counts and other laboratory parameters. This case highlights the diagnostic challenge of differentiating EGPA from HES in patients with persistent eosinophilia and systemic symptoms. Poor response to targeted therapy should prompt re-evaluation for vasculitis. Early recognition and timely immunosuppressive treatment are essential to prevent irreversible organ damage and improve outcomes.