Twenty Years of Undiagnosed Eosinophilia: Diabetic Attribution Bias Delaying Diagnosis of Anca-Positive EGPA Until End-Stage Organ Damage.

INTRODUCTION: Eosinophilic granulomatosis with polyangiitis (EGPA) has the longest diagnostic delay among anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides, with a reported median of 455 days. Cardiac disease, the leading cause of EGPA-related mortality, is largely preventable with early immunosuppression. CASE DESCRIPTION: A 53-year-old Hispanic woman with type 2 diabetes, hypertension, and no documented asthma had 20 years of persistent peripheral eosinophilia (absolute eosinophil count 1-2.7 ×103/μl) and active glomerulonephritic sediment. Eosinophilia was first documented at age 33 when no medical comorbidities existed, predating the diabetes diagnosis by years. Renal function declined from creatinine 0.6 mg/dl (2013) to end-stage renal disease requiring peritoneal dialysis (2024). Ejection fraction fell from 70% (2024) to 20-24% (2026), with left heart catheterization excluding ischemic aetiology. Peripheral neuropathy was attributed to diabetes without electrodiagnostic evaluation. Bone marrow biopsy excluded clonal eosinophilic disorders. ANCA testing, never previously ordered, revealed myeloperoxidase (MPO)-ANCA positivity (>8.0 units, reference 0-0.9) with ANCA IIF titre 1:160 in April 2026. The 2022 American College of Rheumatology / European Alliance of Associations for Rheumatology classification criteria score was ≥6 points without asthma or nasal polyps. Seven missed diagnostic opportunities were identified across multiple specialties and facilities over two decades. CONCLUSION: This case illustrates how "diabetic attribution bias," care fragmentation, and socioeconomic barriers delayed EGPA diagnosis for 20 years despite persistent eosinophilia and progressive multi-organ damage. Systematic ANCA testing in patients with unexplained eosinophilia and organ involvement could prevent irreversible end-organ damage. LEARNING POINTS: Persistent unexplained eosinophilia (absolute eosinophil count >1 ×103/μl) with active glomerulonephritic sediment warrants (ANCA) testing regardless of asthma status, as myeloperoxidase (MPO)-ANCA-positive eosinophilic granulomatosis with polyangiitis (EGPA) may present without prominent asthma and with predominant vasculitic manifestations including glomerulonephritis and peripheral neuropathy."Diabetic attribution bias": the reflexive attribution of organ damage to diabetes in patients with coexisting diabetes. can delay vasculitis diagnosis for years when renal decline and peripheral neuropathy are present alongside atypical features such as improving glycaemic control and active glomerulonephritic sediment.Corticosteroid exposure suppresses eosinophilia in peripheral blood within hours and in body fluids within days, masking the hallmark laboratory finding of EGPA; eosinophil counts and serosal fluid analyses should always be interpreted in the context of recent steroid use.