A 55-year-old Japanese woman with four years history of rheumatoid arthritis (RA) developed muscle weakness, and showed skin ulcers and ischemic colitis. Her renal function was within the normal range except for relatively severe proteinuria. Her serum showed positive results for proteinase 3 (PR3)-anti-neutrophil cytoplasmic antibody (ANCA), but she did not fulfill the diagnostic criteria of ANCA-associated vasculitis syndromes, such as microscopic polyangiitis, Wegener’s granulomatosis, and allergic granulomatous angiitis. Thus, the diagnosis of malignant rheumatoid arthritis (MRA) was made also considering the low level of serum complements. Steroid pulse therapy was not effective, and she developed the perforation of rectum, and died of the subsequent sepsis. Autopsy findings revealed old vasculitis lesions with little inflammatory cell infiltration predominantly showing the destruction of vascular wall structure with following fibrosis, mainly involving small muscular arteries in heart, gastrointestinal tracts, mesenterium, liver, gallbladder, both ovaries and retroperitoneal adipose tissue. Peripheral nerve tissues in the psoas major muscle, however, showed edema, and still exhibited the vascular lesions with active inflammatory cell infiltration. Up to 3% of renal glomeruli showed crescentic glomerulonephritis with the slight deposit of IgM, Clq and C3, revealed with immunohistochemistry. In addition to RA complicated with ANCA-associated vasculitis syndromes, ANCA is sometimes detected in patients of MRA. However, myeloperoxidase-ANCA is almost exclusively detected in such cases, and, as for the cases positive for PR3-ANCA, only one case of histologically proven rheumatoid vasculitis and two cases of RA complicated with Wegener’s granulomatosis have been reported in Western countries. The current case is the first Japanese case of MRA positive for PR3-ANCA.
