Abstract
Fever of unknown origin (FUO) presents a diagnostic challenge, particularly in patients with human immunodeficiency virus (HIV) due to their immunocompromised state. We report a case of a 21-year-old male with HIV who presented with persistent fever and was found to have a positive proteinase-3 antibody, raising suspicion of granulomatosis with polyangiitis (GPA). The patient's symptoms, negative infectious workup, and elevated proteinase-3 levels prompted consideration of non-infectious etiologies. Despite the absence of renal involvement, corticosteroid therapy was initiated, leading to the resolution of fever. However, the false positive association of proteinase-3 in HIV patients introduces uncertainty regarding the definitive diagnosis of GPA. A tissue biopsy would have provided further clarity, but it was not performed in this case. Our workup aligns more closely with a diagnosis of GPA, considering the patient's response to treatment and the absence of clinical deterioration. This case highlights the complexity of diagnosing non-infectious causes of FUO in HIV-infected individuals. It emphasizes the need for a multidisciplinary approach involving infectious disease specialists and rheumatologists to ensure accurate diagnosis and appropriate management.