Fatty change is the abnormal accumulation of triglycerides within parenchymal cells. It is most commonly seen in liver, which is major organ involved in fat metabolism. However, it can also occur in heart, muscles and kidneys.
Main causes are:
- Toxins (alcohol, carbon tetrachloride)
- Protein malnutrition
- Diabetes mellitus
Different mechanisms are involved:
- Alcohol metabolites act as hepatotoxins which alter the mitochondrial and microsomal actions of cells leading to increased synthesis and decreased breakdown of lipids.
- In protein malnutrition and carbon tetrachloride toxin, synthesis of apoproteins is reduced
- In diabetes mellitus and starvation, there is increased mobilization of free fatty acids from peripheral tissues to liver.
- In case of anoxia, fatty acid oxidation is inhibited
- In obesity, with an increased dietary fat intake there is increased transport of free fatty acids to periphery.
In case of mild fatty change, liver may appear to be normal but with progressive accumulation, it enlarges and becomes increasingly yellowish in color. In extreme cases, liver may weigh 6 kg and is transformed into a soft yellow greasy organ.
In mild cases, small vacuoles containing triglycerides appear in cytoplasm around the nucleus.
As the disease progresses, these vacuoles merge to form clear spaces that displace the nucleus towards the periphery.
With more severe disease, adjacent cells rupture and enclosed fat lobules coalesce to form so called fatty cysts.