Resolution of PR3-ANCA-associated vasculitis after antibiotic treatment of subacute bacterial endocarditis: a case report.

Background: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are syndromes categorized by ANCAs and inflammatory infiltration of the walls of small and medium-sized blood vessels. These immunological conditions can destroy valves or result from infections, triggering anti-proteinase 3 (PR3)-ANCA formation. Thus, differentiating infective endocarditis (IE) from AAV is consequential to appropriate management. This case highlights the importance of cardiac workup with AAV due to the presence of valve dysfunction from IE or as a result of a primary vasculitis. Case presentation: A 43-year-old man presented to the clinic with a severe cough for three months, 35-pound unintentional weight loss, and lower extremity petechiae. Labs included an elevated creatinine and a positive ANCA and PR3. Blood cultures were ordered as part of the diagnostic workup for PR3 ANCA vasculitis. They tested positive for Discussion: Subacute endocarditis can be complicated by immune responses that mimic ANCA vasculitis. The European Society of Cardiology recommends evaluation by ECG and echocardiogram in vasculitides. The Vasculitis Foundation notes that in refractory vasculitides, clinicians should evaluate whether infection is mimicking vasculitis. However, there is no guideline for routine blood cultures in AAV. Ultimately, treatment with antibiotics alone led to seronegativity of ANCA and resolution of pathology to the affected extracardiac organs.