Dual myeloperoxidase-antineutrophil cytoplasmic antibody- and antiglomerular basement membrane antibody-positive cases associated with prior pulmonary fibrosis: a report of four cases

Background Both myeloperoxidase-associated antineutrophil cytoplasmic antibody (MPO-ANCA) and antiglomerular basement membrane antibody (anti-GBMAb) positivity have been demonstrated in patients with rapidly progressive glomerulonephritis (RPGN), either with or without pulmonary hemorrhage; however, the implications of these antibodies in such patients have not yet been elucidated. The cases with dual positive antibodies were studied clinically, serologically, and pathologically, and the implications of antibodies are discussed here. Patients and methods Four patients with prior pulmonary fibrosis, who subsequently developed RPGN and pulmonary hemorrhage, were studied clinically, serologically, and pathologically. The clinical data were reviewed extensively and the dual positive antibodies were detected by enzymelinked immunosorbent assays. Pathological studies were performed with a renal biopsy in one patient, a gastric biopsy in another patient, and autopsy materials in the remaining 2 patients. Results All 4 patients had prior pulmonary fibrosis before the symptoms of RPGN when the dual positivity of MPOANCA and anti-GBM Ab was detected. Three cases were accompanied by pulmonary hemorrhage around the time of RPGN whereas the remaining case demonstrated pulmonary hemorrhage a few years later. Renal tissue specimens in 3 cases showed circumferential crescents and linear immunoglobulin G deposits along the glomerular capillary loops in glomeruli. Two autopsy specimens revealed vasculitis of the small arteries and arterioles of the kidney, and one of them showed similar vasculitic findings in both the gastrointestinal tract walls and the adipose tissues of the adrenal glands. Additionally, a case with pulmonary hemorrhage occurring after remission was associated with re-elevated MPO-ANCA levels but without anti-GBM Ab positivity. A gastric biopsy was unremarkable and non-contributory for the diagnosis, but this case showed vasculitic symptoms of peripheral neuritis and retinal hemorrhage. Taken together, all 4 cases demonstrated prior pulmonary fibrosis and dual positivity of MPOANCA as well as anti-GBM Abs at the time of RPGN, and were associated with either pulmonary hemorrhage or its occurrence thereafter. Conclusion Four cases that showed prior pulmonary fibrosis as well as subsequent RPGN and pulmonary hemorrhage were both MPO-ANCA- and anti-GBM Ab-positive at the time of RPGN. The glomeruli disclosed features compatible with anti-GBM Ab disease, but the clinical and pathological vasculitic manifestations, including prior pulmonary fibrosis that might be an early manifestation of ANCA disease, suggested the occurrence of MPO-ANCAassociated vasculitis. Furthermore, 1 case subsequently showed repetitive pulmonary hemorrhage with re-elevated MPO-ANCA positivity but without anti-GBM Ab positivity, and this event was possibly due to MPO-ANCA-associated alveolar capillaritis. As anti-GBM Ab disease is generally thought not to manifest the clinical and pathological features of vasculitis excluding the kidney, MPO-ANCA might be a key factor regarding the occurrence of this dual positive disease.