A case of lymphomatoid granulomatosis with renal involvement.

Lymphomatoid granulomatosis (LYG) is a rare Epstein-Barr virus-associated B-cell lymphoproliferative disorder. While LYG mainly causes pulmonary lesions, it is also known to cause extrapulmonary lesions involving the kidney; however, there are limited reports describing the pathology of extrapulmonary lesions in detail. We report the case of an 82-year-old woman who presented with fever and multiple pulmonary nodules, along with elevated urinary β2-microglobulin and proteinuria. A renal biopsy revealed granuloma-like interstitial infiltrates consisting predominantly of CD3+ and CD4+ T lymphocytes with scattered CD20+ B cells and histiocytes. Similar findings on CT-guided lung biopsy raised the possibility of Grade 1 LYG, although a definitive diagnosis could not be established. Following transient clinical improvement with corticosteroids, pulmonary lesions recurred. Subsequent video-assisted thoracoscopic surgery confirmed the presence of Epstein-Barr virus-encoded small (EBER)-RNA positive cells, establishing a final diagnosis of LYG. Detailed descriptions of the renal pathology of LYG are scarce. This case adds to the limited number of reported cases and highlights the value of renal biopsy in excluding alternative diagnoses, particularly when a definitive diagnosis cannot be made using transbronchial or CT-guided lung biopsy.