# PR3-ANCA Positive Behçet’s Disease with Severe Multisystem Involvement: A Diagnostic Challenge

## TL;DR

A young man with Behçet’s disease showed PR3-ANCA positivity typically seen in GPA, highlighting a diagnostic challenge and the need for tailored treatment.

## Contribution

This case highlights PR3-ANCA positivity in BD as a severe phenotype, not GPA overlap, emphasizing individualized treatment.

## Key findings

- PR3-ANCA positivity in BD may indicate a severe disease phenotype rather than GPA overlap.
- Multisystem involvement in BD requires complex immunosuppressive treatment.
- Diagnostic challenges arise when BD mimics GPA due to PR3-ANCA positivity.

## Abstract

Background: Behçet’s disease (BD) and granulomatosis with polyangiitis (GPA) are distinct vasculitides. PR3-ANCA is considered specific for GPA, yet rare BD cases demonstrate positivity, creating diagnostic dilemmas. Case Presentation: We describe a young man fulfilling criteria for BD, presenting with recurrent oral and genital ulcers, ocular inflammation, catastrophic jejunal perforations, pulmonary embolism, and myocardial infarction with non-obstructive coronary arteries. Despite strong PR3-ANCA positivity, the global phenotype was consistent with BD. Management required a complex, multimodal immunosuppressive regimen that included corticosteroids, cyclophosphamide, therapeutic plasma exchange, and rituximab. Conclusions: PR3-ANCA positivity may represent a severe BD phenotype rather than true GPA overlap, underscoring the need for individualized treatment strategies.