Severe Perinuclear Antineutrophil Cytoplasmic Antibody (p-ANCA)-Positive Granulomatosis With Polyangiitis.

This case report describes a 50-year-old Caucasian male with a history of heroin use and hepatitis C who presented with upper respiratory tract, lower respiratory tract, and renal involvement, ultimately diagnosed with perinuclear antineutrophil cytoplasmic antibody (p-ANCA)-positive granulomatosis with polyangiitis (GPA). The patient initially presented to the emergency department with epigastric pain, leg pain, dyspnea, and hemoptysis, accompanied by recent ear infection, olfactory disturbances, and skin manifestations. Despite initial empiric treatment for suspected pneumonia, his condition rapidly deteriorated. Further investigation revealed elevated inflammatory markers, positive p-ANCA, and characteristic imaging findings including pulmonary nodules and cavitary lesions. Renal involvement was evident through hematuria and proteinuria, while ear, nose, and throat (ENT) examination showed chronic sinusitis and nasal crusting. Renal biopsy revealed pauci-immune necrotizing crescentic glomerulonephritis with evidence of granulomatous inflammation, serologic testing revealed p-ANCA positivity, and negative renal immunofluorescence microscopy results. Treatment was initiated with high-dose glucocorticoids and rituximab, considering the patient's hepatitis C history. This case emphasizes the importance of considering GPA in patients with multi-system involvement, even with p-ANCA positivity, and highlights the complexities of managing patients with significant comorbidities.