Renal amyloidosis associated with extracapillary glomerulonephritis and vasculitis in a patient with inflammatory bowel disease treated with infliximab.

A 70-year-old woman with an 11-year history of indeterminate inflammatory bowel disease developed rapidly progressive glomerulonephritis (RPGN) 3 months after the initiation of infliximab therapy. A renal biopsy showed Congo red-positive homogenous deposits in the mesangial area, glomerular capillary walls and arterial walls. Cellular and fibrocellular crescents were observed in 7 of 28 functioning glomeruli. There were findings of active tubulointerstitial nephritis and vasculitis of the small arteries. On electron microscopy, amyloid fibrils were observed in the deposits. Immunohistochemistry showed positive staining for amyloid A (AA) protein. After cessation of infliximab therapy, she was treated with methylprednisolone pulse therapy followed by oral prednisolone therapy. Thereafter, her RPGN was improved. This is a rare case of co-existent focal extracapillary glomerulonephritis with vasculitis and AA renal amyloidosis. Considering the temporal association of drug use with new onset of RPGN in our patient, we suggest a causal link between infliximab and RPGN due to extracapillary glomerulonephritis and vasculitis.