Introduction
Granulomatosis with polyangiitis (GPA) is a small-medium vessel vasculitis with renal and upper and lower respiratory symptoms. GPA may stay in remission, but may relapse with general symptoms masking/mimicking infection. Anchoring on a wrong etiology delays definitive treatment. Here we present an adult male with history of GPA with overlapping symptoms of infection versus vasculitis flare, ultimately diagnosed with pneumonia and empyema.

Case Presentation
A 62-year-old male with type 2 diabetes mellitus and history of GPA presented with right-sided pleuritic pain. He denied hematuria, sinus problems, rashes, or neuropathy. His GPA had been in remission (last dose of rituximab 3 years ago) and was on maintenance Bactrim. CT Angiogram of the chest showed bilateral lower lobe pneumonia and pleural effusion, and a 13 mm pulmonary nodule. He was discharged on antibiotics but returned the next day for chest pain. Concern for GPA flare was high, but glucocorticoids were avoided given hard to control diabetes. Vasculitis work up and broad-spectrum antibiotics were initiated.

A thoracentesis demonstrated neutrophilic exudate. While the fluid reaccumulated in two days, repeat thoracentesis had lymphocytic exudate. Titers were negative for c-ANCA, p-ANCA, myeloperoxidase, and proteinase-3 (elevated during prior flares). Blood and fluid cultures were negative and without malignant cells. The approval process for avacopan was begun for non-steroidal vasculitis flare treatment. Despite a 7-day course of azithromycin and Rocephin, fluid reaccumulated. A Pleurx catheter was placed, the effusion improved, and patient was discharged on Bactrim while awaiting avacopan.

The patient returned 2 days later with a clogged Pleurx catheter. Subsequent video assisted thoracoscopic surgery revealed an empyema which was evacuated and decortication performed. The pleural fluid grew a beta-lactamase-sensitive Prevoltella and the patient was discharged on Levaquin and Bactrim. Avacopan was not started given lack of systemic vasculitis and improvement with antibiotics and drainage.

Discussion
GPA is a systemic vasculitis of small and medium vessels with necrotizing granulomatous inflammation and pauci-immune vasculitis. A histological diagnosis is the gold standard with supportive serology. Treatment involves induction with DMARDs (Rituxan, Cytoxan, etc.) usually with glucocorticoids, followed by maintenance therapy. Relapse can appear indistinguishable to infection. Because the patient’s disease was not fulminant and the team did not anchor on the vasculitis history, we proceeded with empiric infection treatment and initiated diagnostic workup while avoiding glucocorticoid toxicity or immunosuppression.

Conclusion
This case serves as a demonstration of how GPA in remission masks a diagnosis of empyema. Recognition of anchoring bias is critical to preventing misdiagnosing patients and avoiding adverse outcomes.

References and Resources

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