Hypolipidemia is abnormally low levels of lipids in the blood (see Overview of Cholesterol and Lipid Disorders).
Having a low lipid level rarely causes a problem, but it may indicate the presence of another disorder. For example, a low cholesterol level may indicate an overactive thyroid gland (hyperthyroidism), anemia, undernutrition, cancer, chronic infection, or impaired absorption of foods from the digestive tract (malabsorption). Therefore, doctors may suggest further evaluation when the total cholesterol is less than 120 milligrams per deciliter of blood (mg/dL) or when the low-density lipoprotein (LDL) cholesterol is less than 50 mg/dL. A few rare hereditary disorders, such as abetalipoproteinemia and hypoalphalipoproteinemia, result in lipid levels low enough to have serious consequences.
In abetalipoproteinemia (Bassen-Kornzweig syndrome), virtually no LDL cholesterol is present, and the body cannot make chylomicrons. As a result, the absorption of fat and fat-soluble vitamins is greatly impaired. Symptoms first develop during infancy. Growth is poor. Bowel movements contain excess fat (a condition called steatorrhea), which can make the stools oily, foul smelling, and more likely to float in water. The retina of the eye degenerates, causing blindness (this condition is similar to retinitis pigmentosa). The central nervous system may be damaged, resulting in loss of coordination (ataxia) and intellectual disability. Although abetalipoproteinemia cannot be cured, taking massive doses of vitamin E may delay the development of or slow the damage to the central nervous system.
In hypobetalipoproteinemia, the LDL cholesterol level is very low. Usually, there are no symptoms and no treatment is required. In the most severe form of hypobetalipoproteinemia, almost no LDL cholesterol is present. If family members have the disorder, the diagnosis is more likely. Symptoms and treatment are similar to those of abetalipoproteinemia.
In chylomicron retention disease, a hereditary disorder, the body cannot make chylomicrons. Affected infants tend to develop symptoms similar to those of abetalipoproteinemia. Treatment is supplements of fats and vitamins A, D, E, and K.