Pigments

Lipofuscin

An insoluble pigment, also known as lipochrome or wear-and-tear pigment

Lipofuscin is composed of:

Polymers of lipids and phospholipids in complex with protein

melanin

a normal endogenous brown-black pigment formed by enzymatic oxidation of tyrosine to

dihydroxyphenylalanine in melanocytes

homogentisic acid

a black pigment formed in patients with alkaptouria (lacking homogentisic oxidase) that deposits in skin and connective tissue

anthracosis

accumulations of carbon blacken the tissues of the lungs

anthracosis

Lipofuscin is a telltale sign of

free radical injury and lipid peroxidation

Lipofuscin is prominent in

the liver and heart of aging patients, or patients with severe malnutrition and cancer cachexia

hemosiderin

a hemoglobin-derived, golden yellow-to-brown, granular, or crystalline pigment is one of the major storage forms of iron

lipofuscin granules in cardiac myocytes

example of localized hemosiderosis

common bruise

main causes of hemosiderosis

1. increased absorption of dietary iron
   • due to an inborn error of metabolism called hemochromatosis
2. hemolytic anemia
   • excess lysis of red blood cells leads to release of abnormal quantities of iron
3. repeated blood transfusions

hemosiderosis

when there is systemic iron overload, hemosiderin may be deposited in many organs and tissues

hemosiderosis

pathologic calcification

the abnormal tissue deposition of calcium salts, together with smaller amounts of iron, magnesium, and other mineral salts

forms of pathologic calcification

1. dystrophic calcification
2. metastatic calcification

dystrophic calcification

the deposition of calcium in dead or dying tissue, the serum calcium levels are normal and calcium metabolism is normal

metastatic calcification

the deposition of calcium in normal and healthy tissue. It is seen in hypercalcemia. The serum calcium levels are elevated and the calcium metabolism is abnormal

dystrophic calcification of the aortic valve

four principal causes of hypercalcemia

1. elevated parathyroid hormone
2. bone destruction (reabsorption of bone tissue)
3. Vitamin D related disorders
4. Renal failure