Hypolipidemia is abnormally low levels of lipids in the blood (total cholesterol less than 120 mg/dL [3.1 mmol/L] or low-density lipoprotein (LDL) cholesterol less than 50 mg/dL [1.3 mmol/L]).
Low lipid levels may result from rare genetic abnormalities or other disorders.
People with these genetic abnormalities may have fatty stools, grow poorly, and have intellectual disability.
Some genetic abnormalities are treated with supplements of fats, vitamin E, and other fat-soluble vitamins (vitamins A, D, and K).
(See also Overview of Cholesterol and Lipid Disorders.)
A low level of lipids in the blood may be due to a
Primary cause (a genetic disorder)
Secondary cause (another disorder the person has)
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
Cancer
Chronic infection such as hepatitis C
Impaired absorption of foods from the digestive tract (malabsorption)
Overactive thyroid gland (hyperthyroidism)
Therefore, doctors may suggest further evaluation when blood testing shows that the cholesterol level is very low. The cause, once identified, is treated.
A few rare hereditary disorders, such as abetalipoproteinemia and hypoalphalipoproteinemia, result in lipid levels low enough to have serious consequences. Some people with a mutation in the PCSK9 (proprotein convertase subtilisin/kexin type 9) gene also have low lipid levels, but there are no serious consequences and no treatment is necessary.
Abetalipoproteinemia
In abetalipoproteinemia (Bassen-Kornzweig syndrome), virtually no LDL cholesterol is present, and the body cannot make chylomicrons and very-low-density lipoproteins (VLDL). 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.
The diagnosis is made with blood tests. A biopsy of the intestine is also done. Genetic testing is also done.
Chylomicron retention disease (Anderson disease)
In chylomicron retention disease, a hereditary disorder, the body cannot make chylomicrons. Affected infants tend to develop fat malabsorption, steatorrhea, and failure to thrive and may develop symptoms of central nervous system damage similar to those of abetalipoproteinemia.
Levels of lipids in the blood are measured. In infants whose levels are very low, especially ones that are normally elevated after a meal, a biopsy of the intestine is done.
Treatment is supplements of dietary fats and vitamins A, D, E, and K.
Hypobetalipoproteinemia
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, and people have symptoms similar to those of abetalipoproteinemia.
The diagnosis is made by measuring lipid levels in the blood. If family members have the disorder, the diagnosis is more likely.
Treatment for the most severe form is similar to that of abetalipoproteinemia and includes vitamins A, E, D, and K and supplementation of fat in the diet.
