Elevated Expression of Pentraxin 3 in Anti-neutrophil Cytoplasmic Antibody-associated Glomerulonephritis with Normal Serum C-reactive Protein

A 20-year-old woman was admitted to our hospital with an elevated serum creatinine level of 1.61 mg/dL and a normal C-reactive protein level of less than 0.1 mg/dL. Her myeloperoxidase anti-neutrophil cytoplasmic antibody (ANCA) titer was slightly increased at 9.2 U/mL; a kidney biopsy revealed that 23 of 32 glomeruli had crescents. The expression of pentraxin 3 was detected in her kidney and her plasma pentraxin 3 level was elevated at 63.53 ng/mL. Plasma pentraxin 3 levels may be an activity marker for ANCA-associated glomerulonephritis, particularly when serum C-reactive protein levels are within the normal limits.