Granulomatosis with Polyangiitis Presenting as ANCA-Negative Pulmonary Disease with Distributive Shock

Background: Granulomatosis with polyangiitis (GPA) is an antineutrophil cytoplasmic antibody (ANCA)-associated necrotizing vasculitis primarily affecting small and medium-sized vessels. The typical presentation commonly includes upper and/or lower respiratory tract and renal involvement. GPA has a particularly strong association with proteinase-3 (PR3) ANCA. Though well defined, GPA may be clinically difficult to recognize, particularly in early disease. Initial presentations may include nonspecific symptoms, including but not limited to fatigue, fever, and sinus congestion or sinusitis, which may be mistaken for infection. Though initial ANCA testing is useful, it is not definitive as early stages of disease may be negative, thus delaying diagnosis; Clinical Significance: This case highlights the importance of including GPA in the differential diagnosis of patients with unremitting upper or lower respiratory and constitutional symptoms despite negative ANCA testing. Though atypical, GPA cases may lack renal involvement and even have negative ANCA serologies, leading to a delay in diagnosis and increased morbidity. ANCA positivity can be as low as 60% in limited GPA cases, and less than 20% of individuals have renal involvement at presentation. If GPA suspicion is high, repeat testing and biopsy are warranted; Case Presentation: A woman in her 50s initially presented to the emergency department with recurrent/persistent fever with nonspecific sinus symptoms that remained unresolved despite multiple outpatient treatments and tests. Infectious work-up was negative. She was found to have multiple pulmonary nodules on various scans. Initial testing on admission was unremarkable or nondiagnostic, including anti-neutrophil cytoplasmic antibody (ANCA) serologies. The patient's hospital course was complicated by acute hypoxic respiratory failure with distributive shock during bronchoscopy. Repeat serological testing was positive for PR3-ANCA, and lung biopsy demonstrated necrotizing granulomatous vasculitis consistent with a diagnosis of granulomatosis with polyangiitis (GPA). The patient demonstrated clinical improvement with avacopan, glucocorticoids, and rituximab; Conclusions: The diagnosis of GPA should be suspected in all patients with nonspecific constitutional symptoms along with clinical evidence of upper/lower respiratory tract involvement, regardless of renal function. Physicians with a strong suspicion of an autoimmune disease, such as GPA, should utilize a thorough clinical history, physical exam, and other labs in the setting of a negative autoimmune marker and/or negative imaging. Clinical judgment is required to not rule out GPA despite a negative workup when other more serious causes have been excluded, as the diagnosis may be life-threatening.