Infective Endocarditis-Associated Pauci-Immune Glomerulonephritis in a Patient With Cryoglobulinemia.

Small-vessel vasculitis has a broad differential with similar clinical presentation and laboratory abnormalities, including petechial rashes, neurologic symptoms, glomerulonephritis, and abnormal inflammatory markers. Biopsy-based diagnosis is critical as the treatment varies by etiology. We report a case of a 41-year-old man with diagnosed cryoglobulinemia and hepatitis C presenting with a petechial rash, altered mental status, and acute kidney injury and ultimately found to have proteinase 3 (PR3)-antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis secondary to infective endocarditis. Skin biopsy was consistent with resolving, but nonspecific vasculitis and MRI showed foci of hemosiderin deposition concerning vasculitic lesions. Blood cultures grew Enterococcus faecalis, and he was treated with IV antibiotics. Kidney biopsy showed pauci-immune necrotizing focal segmental glomerulonephritis (GN) and diffuse acute tubular necrosis (ATN). After blood cultures cleared, he was initially treated with mycophenolate for worsening renal function. When the patient stopped antibiotics unexpectedly, his kidney function worsened and improved only after immunosuppression was stopped and antibiotics were restarted. This case highlights the importance of renal biopsy in patients with multiple potential etiologies of GN. The case resolution also reinforces that patients with infective endocarditis causing ANCA-associated GN should be treated with antibiotics in addition to, and possibly instead of, immunosuppression.