Reversible cellular changes & accumulations

Even though there are many different kinds of reversible cellular changes & accumulations, here we will only mention fatty change & accumulation of pigments.

1. Fatty change

 This is accumulation of triglycerides inside parenchymal cells. It is caused by an imbalance between the uptake, utilization, & secretion of fat. Fatty change is usually seen in the liver, heart, or kidney. Fatty liver may be caused by alcohol, diabetes mellitus, malnutrition, obesity, & poisonings. These etiologies cause accumulation of fat in the hepatocytes by the following mechanisms: 

a.  Increased uptake of triglycerides into the parenchymal cells. 

b.  Decreased use of fat by cells. 

c.  Overproduction of fat in cells. 

d. Decreased secretion of fat from the cells.

2. The accumulations of pigments 

 Pigments can be exogenous or endogenous. Endogenous pigments include melanin, bilirubin, hemosiderin, & lipofuscin. Exogenous pigments include carbon. These pigments can accumulate inside cells in different situations.

a. Melanin

 Melanin is a brownish-black pigment produced by the melanocytes found in the skin. Increased melanin pigmentation is caused by suntanning & certain diseases e.g. nevus, or malignant melanoma. Decreased melanin pigmentation is seen in albinism & vitiligo.

b.  Bilirubin

 Bilirubin is a yellowish pigment, mainly produced during the degradation of hemoglobin. Excess accumulation of bilirubin causes yellowish discoloration of the sclerae, mucosae, & internal organs. Such a yellowish discoloration is called jaundice. 

Jaundice is most often caused by 

1. Hemolytic anemia

Hemolytic anemia is characterized by increased destruction of red blood cells.

 2. Biliary obstruction

This is obstruction of intrahepatic or extrahepatic bile ducts. It can be caused by gallstones.

3. Hepatocellular disease

This is associated with failure of conjugation of bilirubin.

 C. Hemosiderin

Hemosiderin is an iron-containing pigment derived from ferritin. It appears in tissues as golden brown amorphous aggregates & is identified by its staining reaction (blue color) with the Prussian blue dye. Hemosiderin exists normally in small amounts within tissue macrophages of the bone marrow, liver, & spleen as physiologic iron stores. It accumulates in tissues in excess amounts in certain diseases.This excess accumulation is divided into 2 types:

1.  Hemosiderosis

When accumulation of hemosiderin is primarily within tissue macrophages & is not associated with tissue damage, it is called hemosiderosis.

2. Hemochromatosis

When there is more extensive accumulation of hemosiderin, often within parenchymal cells, which leads to tissue damage, scarring & organ dysfunction, it is called hemochromatosis.

References

Bezabeh ,M. ; Tesfaye,A.; Ergicho, B.; Erke, M.; Mengistu, S. and Bedane,A.; Desta, A.(2004). General Pathology. Jimma University, Gondar University Haramaya University, Dedub University.