[Two Sides of the Same Coin: Eosinophilic Granulomatosis with Polyangiitis or Hypereosinophilic Syndrome - A Case Report].

BACKGROUND

Mild and persistent peripheral eosinophilia is a common laboratory finding, often of unclear significance. However, it may represent an early sign of a hypereosinophilic disorder, such as Hypereosinophilic syndrome (HES) or Eosinophilic granulomatosis with polyangiitis (EGPA). These entities share overlapping clinical and laboratory features, rendering the differential diagnosis challenging especially at initial presentation.

OBJECTIVES

A 19-year-old female began her clinical course at 15 years of age with asthma-like respiratory symptoms and received conventional and biologic therapies for asthma. Over time, her condition progressively deteriorated, characterized by escalating eosinophil counts, worsening respiratory symptoms, and evidence of multisystem involvement, including pulmonary, cardiac, cutaneous, and central nervous system manifestations. Extensive evaluation left the diagnosis unresolved between EGPA and HES, given the absence of overt vasculitis or ANCA (Antineutrophil Cytoplasmic Antibodies) positivity, along with overlapping clinical features. Systemic corticosteroids resulted in rapid symptom improvement, but relapses occurred upon dose reduction. Eventually, she was treated with a combination of Rituximab (anti-CD20 monoclonal antibody) and Mepolizumab (anti-IL-5 monoclonal antibody), leading to complete disease control: normalization of eosinophil counts, significant improvement in pulmonary function, resolution of neurological symptoms, and successful corticosteroid tapering.

DISCUSSION: This case illustrates the diagnostic complexity posed by hypereosinophilic conditions with overlapping phenotypes and underscores the evolving therapeutic landscape in eosinophilic disorders.