[Case of immune complex crescentic glomerulonephritis with consistently high titers of MPO-ANCA for 6 years].

A male patient, now 65 years old, experienced fever, hemoptysis, and respiratory failure about six years ago. Soon thereafter, he developed rapid progressive renal dysfunction with pulmonary hemorrhage and positive findings for MPO-ANCA. We commenced methylprednisolone pulse (MP) therapy followed by oral prednisolone (PSL) and intravenous cyclophosphamide (CY) for the treatment of ANCA-associated microscopic polyangiitis (MPA). Therapeutic efficacy was obtained comparatively rapidly. Light microscopic findings of a percutaneous renal biopsy demonstrated focal necrotizing and crescentic glomerulonephritis. Immunofluorescent microscopy indicated diffuse deposition of IgG and C3 along the periphery of the tufts and in the mesangium. On the basis of these findings, the condition was diagnosed as immune complex crescentic glomerulonephritis associated with MPO-ANCA. MPO-ANCA titers were high (714 EU) at onset and remained high (250-450 EU) over the ensuing 6 years with oral administration of PSL 5 mg. Though his condition remitted completely, his MPO-ANCA titers recently increased to above 600 EU once more. We conducted a follow-up renal biopsy to ascertain if the fluctuation of MPO-ANCA titers reflected an early stage of relapse. Light microscopic findings of the biopsied tissue revealed no signs of necrosis or crescentic formation of the glomeruli. Immunofluorescent microscopic findings were negative. The elevated MPO-ANCA titers were not valuable for the early prediction of relapse in our case, and the immune complex may have played an important role. When judging relapse and remission in ANCA-associated glomerulonephritis, it is important to evaluate the overall clinical findings and histopathological findings in addition to the serial ANCA titers.