Infective Endocarditis-Associated Glomerulonephritis With Cryoglobulin Positivity.

backgroundSerum cryoglobulins are frequently elevated in cases of infective endocarditis-associated glomerulonephritis (IEAGN). We report a case of cryoglobulin-positive IEAGN, initially diagnosed as cryoglobulinemic glomerulonephritis. CASE SUMMARY: A woman in her 70s visited our hospital with a rapidly declining renal function. Cryoglobulins were detected in her blood sample, and findings of the renal biopsy initially indicated cryoglobulinemic glomerulonephritis. Despite initiating steroid therapy, her renal function did not improve. Further investigations, including an echocardiogram, revealed mitral valve vegetation, and blood cultures identified a gram-positive coccus. These findings led to a revised diagnosis of IEAGN. After the initiation of antimicrobial therapy, the patient's serum cryoglobulin levels normalized, and her renal function improved. DISCUSSION: Cryoglobulinemia is frequently observed in cases of IEAGN, but these cryoglobulins are often clinically insignificant and tend to resolve with appropriate antimicrobial therapy. TAKE-HOME MESSAGE: In the case of cryoglobulin-positive nephritis, the possibility of IEAGN should always be considered, requiring careful differentiation from other cryoglobulin-associated diseases.