Dual ANCA positivity in subacute bacterial endocarditis

Area of Science:

• Rheumatology
• Infectious Diseases
• Immunology

Background:

• Subacute bacterial endocarditis (SBE) is a serious infection typically associated with specific risk factors.
• Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a distinct clinical entity.
• Previous literature documented SBE cases associated with anti-PR3 ANCA, but not dual positivity.

Observation:

• Two patients presented with SBE and dual ANCA positivity (anti-PR3 and anti-MPO ANCA).
• One patient had concurrent cutaneous vasculitis; the other had SBE predisposing factors.
• ANCA titers decreased with corticosteroid treatment for suspected vasculitis.

Findings:

• These are the first reported cases of SBE associated with dual anti-PR3 and anti-MPO ANCA.
• Follow-up excluded common ANCA-associated vasculitides like Wegener granulomatosis.
• ANCA positivity in SBE may mimic or overlap with vasculitis presentations.

Implications:

• Rheumatologists should consider SBE in patients with ANCA positivity, especially dual positivity.
• Recognizing this association can prevent unnecessary and potentially harmful immunosuppressive therapy.
• This finding highlights the complex interplay between infection and autoimmune markers.