Histiocytic and Nonhistiocytic Glomerular Lesions: Foam Cells and Their Mimickers

Numerous histiocytes are sometimes noted in glomeruli, giving rise to a foamy-appearing glomerulus. Foamy-appearing glomeruli may also be noted in conditions that do not contain numerous histiocytes. These disease entities are rare, have different underlying causes and pathophysiology, and can cause a diagnostic dilemma. We have observed this histiocytic/foamy glomerular change on the kidney biopsy specimen in 5 different disease entities: crystal-storing histiocytosis, histiocytic glomerulopathy associated with macrophage-activating syndrome, thrombotic microangiopathy, lecithin-cholesterol acyltransferase deficiency, and lipoprotein glomerulopathy. We describe and compare the kidney biopsy findings of these histiocytic and foamy-appearing entities. It is important to recognize the kidney biopsy findings of these rare conditions to correctly evaluate and identify the cause and manage these patients.