Lipofuscin

Lipofuscin is a blue to black granular cytoplasmic material noted in many organs (Figures 9.3, 9.17a, b). It is the result of incomplete digestion of lipids and lipoproteins. In rats, chemical inhibition of lysosomal proteases will increase lipofuscin deposition in the liver; in other species it is thought to have minimal pathologic significance and increases are noted with age (Kitani et al., 1989; Scott, 2006). Lipofuscin is acid-fast and will stain positive with the Schmorl reaction. In addition, lipofuscin will autofluoresce.