LAUSR

Xanthogranulomatous pyelonephritis (XGP) is a rare chronic infectious process of the kidney that results in diffuse destruction of the renal parenchyma [1,2]. The majority of cases of XGP occur in the setting of obstructing nephrolithiasis and are histologically characterized by the presence of lipid-laden foamy macrophages. To date, little is known regarding the molecular and functional phenotype of the infiltrating macrophages observed in cases of XGP. Human CD14+ monocytes can differentiate into macrophages and then become polarized towards two distinct phenotypes [3–5]. Classically activated (also known as M1) macrophages have the ability to secrete pro-inflammatory cytokines such as IFN-γ, IL-2, and TNF-α. Conversely, alternatively activated (also known as M2) macrophages secrete anti-inflammatory cytokines such as IL-10, IL-23, and VEGF. Characterization of the immune infiltrate in cases of XGP is necessary for understanding the pathogenesis of this disease process. Moreover, this knowledge may form the basis of future non-invasive treatment strategies for XGP. Herein, we report the phenotypic characterization of the macrophage infiltrate in a case of XGP.