Bacterial endocarditis manifesting as autoimmune pulmonary renal syndrome: ANCA-associated lung hemorrhage and pauci-immune crescentic glomerulonephritis .

The etiology of pulmonary renal syndrome can be broadly divided into infectious and autoimmune (predominantly ANCA vasculitis). The importance of timely differentiating between them stems from the deleterious effects of their respective treatment if misdiagnosed. Serology and tissue evaluation by pathology are employed to aid in this, however, in rare cases, this can be difficult. We present a case of infectious endocarditis that presented with pulmonary renal syndrome but had positive ANCA serology and a pauci-immune glomerulonephritis picture on kidney biopsy that posed diagnostic difficulty. Factors most helpful in differentiating between the two conditions are highlighted as well as treatment options. .