Cellular Pigments and Their Accumulation

Key points

• • Pigments are coloured substances that can accumulate in cells; they may be made by the body (endogenous) or come from outside (exogenous).
• • Melanin is the brown-black pigment that colours skin and hair and protects against ultraviolet light, and too little or too much causes recognisable disorders.
• • Lipofuscin is a yellow-brown wear-and-tear pigment that builds up in ageing or wasting cells, especially in the heart and liver.
• • Haemosiderin is a golden-brown iron-storage pigment; a local build-up marks old bleeding (as in a bruise), while a body-wide build-up occurs in iron overload.
• • Bilirubin, the pigment from the breakdown of haemoglobin, builds up in jaundice and stains the tissues yellow.
• • Carbon (soot) breathed in from polluted air is the commonest exogenous pigment, collecting in the lungs and their lymph nodes as anthracosis.