Abstract Introduction Eosinophilic granulomatosis with polyangiitis (EGPA) is a multisystem vasculitis characterized by asthma, rhinitis and eosinophilia. While pulmonary manifestations are diverse, bronchial casts containing Charcot-Leyden crystals, which reflect eosinophilic breakdown, are rarely reported. Diagnostic process is often challenging, particularly in seronegative EGPA with isolated pulmonary disease where it mimics other eosinophilic lung diseases. We present a case of seronegative EGPA initially diagnosed as chronic eosinophilic pneumonia (CEP), with the definitive diagnosis established when vasculitic features developed after steroid discontinuation. Case Description A 59-year-old Chinese female, never-smoker, with hypertension, diabetes mellitus and endometrial cancer (in remission), presented with a 9-month history of worsening dyspnea, cough and expectoration of thick, whitish plugs. Six months before presentation, she was treated with antibiotics for pneumonia and a brief course of prednisolone for concurrent wheeze. Serial chest imaging revealed migratory pulmonary infiltrates. CT thorax showed bilateral ground glass opacities with crazy-paving and bronchial wall thickening. Bronchoscopy revealed dense bronchial casts, with histology demonstrating Charcot-Leyden crystals with abundant eosinophils and fibrinous material. Bronchoalveolar lavage was negative for bacterial, mycobacterial and fungal pathogens. Complete blood count demonstrated eosinophilia (absolute eosinophil count, 1.16 x 109/L). Extensive work-up including allergic bronchopulmonary aspergillosis screen, parasitic studies and autoimmune serologies (anti-neutrophil cytoplasmic, anti-myeloperoxidase and anti-proteinase 3 antibodies) were negative. Fractional exhaled nitric oxide was markedly elevated at 176 ppb. Spirometry, lung volumes and diffusion studies were normal. A diagnosis of CEP with concurrent asthma was made. She was discharged on Fluticasone propionate/Salmeterol inhaler and oral prednisolone (0.5mg/kg/day). Her prednisolone was gradually tapered with improvement in symptoms, radiology and peripheral eosinophilia. However, a month after discontinuation of prednisolone, she was hospitalized for bilateral lower limb weakness, numbness and painful palpable purpuric nodules. Skin biopsy revealed dermal eosinophilia and nerve conduction studies confirmed mononeuritis multiplex. Her diagnosis was revised to seronegative EGPA. Induction therapy with pulsed intravenous methylprednisolone and cyclophosphamide was started with clinical improvement. Discussion Up to 70% of EGPA patients are seronegative and typically have a predominantly eosinophilic phenotype. This case highlights the complexity of distinguishing CEP from the isolated pulmonary phase of seronegative EGPA. In our case, the presence of bronchial casts with Charcot-Leyden crystals, while rare, may signal unusually intense eosinophilic inflammation, potentially beyond typical CEP. This underscores the importance of vigilant monitoring for emergence of new systemic features as it mandates escalation of immunosuppressive therapy to prevent irreversible systemic complications. This abstract is funded by: None
Lee et al. (Fri,) studied this question.