Microscopic polyangiitis with histopathologic evolution in serial renal biopsies during treatment of idiopathic
Yuya Yamaguchi1, Takeshi Tosaki1,2, Takaya Sasaki3,4
1Department of Nephrology, Kawaguchi Municipal Medical Center, Saitama, Japan.
Abstract:
Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease associated with inflammation implicated in the development of vasculitis, specifically microscopic polyangiitis (MPA). Herein, we report a case of MPA complicated by IPF. A woman in her 70s with a history of IPF treated with nintedanib presented with a serum creatinine level of 2.22 mg/dL, microscopic hematuria, and a serum myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA) titer level of 78.5 IU/mL. The initial renal biopsy revealed diffuse tubulointerstitial nephritis without glomerular crescent formation; therefore, prednisolone was initiated. However, the serum MPO-ANCA titer level increased to 91.1 IU/mL after tapering the prednisolone dose. A second renal biopsy revealed pauci-immune necrotizing glomerulonephritis with crescents, confirming MPA. Treatment was adjusted to include a resumed steroid regimen and combination therapy with rituximab and avacopan, resulting in stable kidney function. In conclusion, this case underscores the importance of monitoring serum ANCA titer levels as a surrogate marker for subclinical vasculitis in patients with IPF. The sequential occurrence of tubulointerstitial nephritis followed by crescentic glomerulonephritis suggests a potential progression pattern in MPA, warranting careful clinical and histopathological evaluations.
Insights
Idiopathic pulmonary fibrosis (IPF) patients require monitoring for microscopic polyangiitis (MPA). Early detection of MPA, indicated by myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA) levels, is crucial for timely intervention and stable kidney function.
Area of Science:
- Nephrology
- Pulmonology
- Rheumatology
Background:
- Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease linked to inflammation and vasculitis.
- Microscopic polyangiitis (MPA) is a form of vasculitis that can complicate IPF.
- Patients with IPF may develop MPA, necessitating careful monitoring of renal function and inflammatory markers.
Purpose of the Study:
- To report a case of MPA complicating IPF.
- To highlight the importance of monitoring MPO-ANCA titers in IPF patients.
- To describe the diagnostic and therapeutic challenges in managing co-existing IPF and MPA.
Main Methods:
- Case report of a woman in her 70s with IPF.
- Initial presentation with elevated creatinine, hematuria, and positive MPO-ANCA.
- Sequential renal biopsies, treatment adjustments including steroids, rituximab, and avacopan.
Main Results:
- Initial renal biopsy showed tubulointerstitial nephritis; treatment with prednisolone was initiated.
- Rising MPO-ANCA titers and a second biopsy confirmed pauci-immune necrotizing glomerulonephritis (MPA).
- Combination therapy with steroids, rituximab, and avacopan stabilized kidney function.
Conclusions:
- Monitoring MPO-ANCA titers is vital for detecting subclinical MPA in IPF patients.
- The progression from tubulointerstitial nephritis to crescentic glomerulonephritis may represent a pattern in MPA.
- Integrated clinical and histopathological assessment is crucial for managing complex cases of IPF with MPA.
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