In addition, because the anti-GBM antibody titer has been reported to reflect the disease activity of Goodpasture syndrome (10), and because the lung disease was not aggravated even when the kidney disease activity increased, it would be difficult to attribute this lung disease (including the kidney disease) to Goodpasture syndrome. BMS-536924 In conclusion, we reported a possible case of the sequential development of anti-GBM nephritis due to MPO-ANCA-associated vasculitis in the clinical setting. The authors state that they have no Conflict of Interest (COI).. collagen (1). The normal structural configuration of type IV collagen hexamers in the GBM prevents antigen-antibody interactions. Hydrocarbon exposure, smoking, and infections, such as flulike illness, are associated with the disclosure of the hidden antigen (2, 3). Anti-GBM nephritis is usually possibly caused by antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis because ANCA has a strong membrane-disordering action. Some case reports have already indicated the sequential development of anti-GBM nephritis and ANCA-associated vasculitis (4, 5). To the best of our knowledge, there are no reports on anti-GBM nephritis induced by ANCA-associated vasculitis in the clinical setting. We herein report a possible case of the sequential development of anti-GBM nephritis due to myeloperoxidase (MPO)-ANCA-associated vasculitis in the clinical setting. Case Report A 55-year-old woman with no history of diabetes mellitus complained of bilateral earache and was treated by an otorhinolaryngological practitioner in November 2014. Although her serum creatinine (sCr) level was within the normal limits (0.61 mg/dL), her C-reactive protein (CRP) level was slightly elevated (0.61 mg/dL), and her urine test results were as follows: protein, 1+; occult blood, 3+; and urinary sediment of red blood cells, 300 /L, from the beginning CD69 of February 2015. The patient was referred to the Department of Otorhinolaryngology in our hospital after her bilateral earache became aggravated in late February 2015. MPO-ANCA-associated otitis media was BMS-536924 suspected because of sensory deafness and a high MPO-ANCA titer (>300 U/mL) (normal range, <3.5 U/mL). The patient was referred to our Department of Nephrology and was admitted in the beginning of March 2015 because of renal insufficiency (sCr, 0.89 mg/dL) with CRP level elevation (4.99 BMS-536924 mg/dL), proteinuria (3+), and hematuria (3+). On admission, her blood pressure was 123/76 mm Hg and she had a regular pulse rate (105 beats/min). Her height and body weight were 151 cm and 55.5 kg, respectively. Her body temperature was slightly elevated (37.7). With the exception of bilateral hearing loss, the findings of physical examination were unremarkable. A serum analysis revealed the following findings: white blood cells, 13,410 /L; hemoglobin, 11.7 g/dL; platelets, 34.2104/L; urea nitrogen, 10.8 mg/dL; sCr, 1.10 mg/dL; CRP, 8.75 mg/dL; albumin, 3.1 g/dL; hemoglobin A1c, 5.3%; MPO-ANCA, >300 U/mL, and proteinase 3 (PR3)-ANCA, <1.0 U/mL (normal range, <3.5 U/mL). Her urine test results were as follows: protein, 2+; daily urinary protein excretion, 1.51 g/gCr; occult blood, 3+; urinary sediment of red blood cells, 411 /L; urinary N-acetyl--D-glucosaminidase (NAG), 17.2 U/mL, and urinary 2-microglobulin, 29,622 g/L (Table). Although chest computed tomography did not show alveolar hemorrhage, a slight reticular shadow was detected in the bilateral lower lungs. Table. Laboratory Findings on Admission. HematologyBlood ChemistryImmunologyWBC13,410/LNa135 mEq/LCRP8.75 mg/dLRBC402104/LK3.7 mEq/LC374 mg/dLHb11.7 g/dLCl97 mEq/LC429 mg/dLHct36.1%Ca8.9 mg/dLCH5060 U/mLPlt34.2104/LPi2.4 mg/dLIgG2,039 mg/dLBUN10.8 mg/dLIgA497 mg/dLsCr1.10 mg/dLIgM82 mg/dLUA4.7 mg/dLANA (<40)160T-Bil0.7 mg/dLMPO-ANCA (<3.5)>300 U/mLAST16 U/LPR3-ANCA (<3.5)<1.0 U/mLALT10 U/LUrinalysisLDH148 U/LProtein2+CPK32 U/LProtein excretion1.51 g/gCrALP179 U/LSugar?ChE174 U/LOccult blood3+TP7.7 g/dLSediment of RBC411 /LAlb3.1 g/dLNAG (0.7-11.2)17.2 U/mLHbA1c5.3%2 MG (<230)29,622 g/L Open in a separate window The data in parentheses means normal range in each laboratory finding. BUN: blood urea nitrogen, sCr: serum creatinine, UA: uric acid, T-Bil: total bilirubin, AST: aspartate aminotransferase, ALT: alanine aminotransferase, LDH: lactate dehydrogenase, CPK: creatine phosphokinase, ALP: alkaline phosphatase, ChE: choline esterase, TP: total protein, Alb: albumin, HbA1c: hemoglobin A1c, CRP: C-reactive protein, CH50: complement activity, Ig: immunoglobulin, ANA: BMS-536924 antinuclear antibody, ANCA: antineutrophil cytoplasmic antibody, MPO: myeloperoxidase, PR3: proteinase 3, BMS-536924 NAG: N-acetyl–D-glucosaminidase, 2 MG: 2-microglobulin MPO-ANCA-associated vasculitis was considered based on the systemic inflammatory findings (fever and an increased serum CRP level), the presence of otitis media, the reticular shadow in her lungs and rapidly progressive glomerulonephritis, and her high MPO-ANCA titer. Thus, steroid therapy [oral prednisolone (40 mg, daily)] was initiated a day after admission. Renal biopsy was performed 9 days after admission and revealed cellular crescents in 41% of the glomeruli with segmental fibrinoid necrosis (Fig. 1A). Widespread tubular atrophy and interstitial fibrotic changes were present with diffuse mononuclear cell infiltration (Fig. 1B), and peritubular capillaritis was occasionally observed (Fig. 1C). Immunofluorescence microscopy showed linear deposits of immunoglobulin G along the GBM (Fig. 1D). No C3 staining was found in the immunological examination (data not shown). The anti-GBM antibody level in a remaining serum sample that had been collected around the admission day was 11.7 U/mL (normal limits, <3.0 U/mL). In addition, the anti-GBM antibody level was remarkably elevated to 127 U/mL at 10 days after admission. The reticular shadow in the lungs was not aggravated in parallel with the increase in the patient's anti-GBM antibody. In contrast, the patient experienced rapidly progressive renal dysfunction caused again when an increase.