Foam cells Abnormal renal insterstitial morphology Renal interstitial foam cells FCs are the outcome of cellular lipid accumulation due to lipid metabolic dysfunction. Normally, lipid is in a dynamic equilibrium outside and inside of the cell. When factors facilitate cell lipid intake or reduce its efflux, it subsequently resulted in cellular lipid accumulation and FC formation. Renal interstitial FCs are commonly encountered in Alport syndrome and are occasionally observed in various other kidney diseases, including idiopathic membranous nephropathy (IMN), IgA nephropathy (IgAN), focal and segmental glomerulosclerosis (FSGS), and membranoproliferative glomerulonephritis. Accumulation of foam cells (FC) in the interstitium of the kidney. Renal FCs display phenotypic characteristics of macrophages and belong to the monocyte/macrophage lineage. Histologically, renal FCs are characterized by round cells with small nuclei and an abundant PAS-positive cytoplasm with lipid-containing vacuoles.