Lipofuscin (age pigment) is a brown-yellow, electron-dense, autofluorescent material that accumulates progressively over time in lysosomes of postmitotic cells, such as neurons and cardiac myocytes. This term pertains if there is an increase in the accumulation of lipofuscin (also known as autofluorescent lipoprotein) more than expected for the age of the patient. [from
HPO]