Macrophage Infiltration into the Glomeruli in Lipoprotein Glomerulopathy

Lipoprotein glomerulopathy (LPG) is characterized by histopathological features showing intra-glomerular lipoprotein thrombi and type III hyperlipoproteinemia (HLP), with heterozygote mutation of apolipoprotein (apo) E gene. On the other hand, as another renal lipidosis with type III HLP, apoE2 homozygote-related glomerulopathy (apoE2-GN) showing foamy macrophages has been reported. The case of a 25-year-old man who had LPG by clinical behavior and gene analysis, but demonstrated atypical histopathological features with a substantial amount of foamy macrophage infiltration in the glomeruli, is presented. The combination of alleles for apoE Tokyo/Maebashi and classical apoE2 (Arg158Cys) was inferred to be the leading cause of the unique renal pathology with lipoprotein thrombi and foamy macrophages. In addition, foamy macrophages infiltrated some part of the apoE-positive region within the glomerulus, but did not exist in lipoprotein thrombi despite apoE positivity, suggesting that properties of apoE are crucial in the development of LPG rather than macrophage function. This case provides important information related to the pathogenesis of LPG and apoE2-GN.