Immunohistochemical characterization of granulomatosis with polyangiitis exhibiting spontaneous regression.

Background: Granulomatosis with polyangiitis (GPA) is characterized by granulomatous inflammation, vasculitis, and elevated levels of serum proteinase 3 (PR3)-anti-neutrophil cytoplasmic antibody (PR3-ANCA).
Objective: We tried to characterize immune cells accumulated into the lung lesions of a GPA patient exhibiting spontaneous regression.
Methods: Transbronchial lung biopsy (TBLB) samples were subjected to immunohistochemical analyses.
Results: Multiple lung nodules were detected by CT. TBLB showed granulomatous inflammation and small vessel vasculitis. This case was diagnosed as GPA based on pathological findings and elevation of PR-3 ANCA levels. Spontaneous disappearance of multiple lung nodules was observed in CT. CD3+ T cells and CD20+ B cells accumulated in the inflammatory lesions surrounding the vessels whereas granulomatous inflammation was mainly comprised of CD3+ T cells and CD68+ macrophages, but not B cells or myeloperoxidase+ neutrophils.
Conclusions: We characterized immune cell compositions of the lung lesions of a patient with GPA exhibiting spontaneous regression.