A group of rare genetic disorders characterized by deficient activity of an enzyme (lipoprotein lipase) that breaks down fat molecules, causing the accumulation of large quantities of fat (lipoproteins) in the blood.
Alternative Names
Type I hyperlipoproteinemia; Familial chylomicronemia
Causes, incidence, and risk factors
A defective gene is usually the cause of this disorder, which is inherited in an autosomal recessive manner. Blood tests show an elevation of chylomicrons, a type of lipoprotein, which are small droplets of fat made in the small intestine that carry fats from digested food into the blood stream. The chylomicrons are not broken down normally because of the deficiency of the lipoprotein lipase enzyme . This results in a build up of fat-laden chylomicrons in blood such that the serum appears pale and creamy. Skin lesions (xanthomas) form as a result of deposits of these chylomicrons in the skin. There is inflammation of the pancreas and resulting abdominal pain . Risk factors are a family history of lipoprotein lipase deficiency, very high triglycerides in the blood, unexplained, multiple episodes of pancreatitis , and failure to thrive in infancy. The incidence is 1 out of 1,000,000 people. The disease usually becomes apparent in infancy or early childhood.
Signs and tests
A physical examination reveals xanthomas, an enlarged liver , an enlarged spleen , and jaundice may be evident. An eye examination reveals pale retinas and whitish retinal vessels. Tests that may indicate this disorder is present include:
milky appearing serum/plasma from blood. a special test showing absent or decreased lipoprotein lipase activity in blood collected after treatment with intravenous heparin. markedly elevated triglycerides in blood.
elevation of cholesterol and total fat in blood. failure to remove chylomicrons from blood more than 12 hours after a meal. an overnight icebox test showing chylomicrons in fasting serum. an apolipoprotein CII deficiency may cause a rare subset of this disease in people with normal lipoprotein lipase activity.
genetic testing may reveal a mutation(s) in the genes for lipoprotein lipase or apolipoprotein CII.
Treatment
The purpose of treatment is to control the symptoms and blood triglyceride levels by a very low fat diet. Fat intake usually must be less than 20 grams per day for the symptoms not to recur. 20 grams of fat is equivalent to 1 of the following: 2 - 8 ounce glasses of whole milk, 4 teaspoons of margarine, or a 4 ounce serving of meat. The average American diet has an average fat content of up to 45% of total calories. Fat-soluble Vitamins A, D, E, and K and mineral supplementation is recommended. Dietary counseling is helpful for patients to adhere to a restrictive diet and maintain adequate calorie and nutrient intake. Pancreatitis responds to conventional treatments for that disorder.
Expectations (prognosis)
By following a diet in which fat is restricted people can live into adulthood.
Complications
Pancreatitis and recurrent episodes of abdominal pain may develop. Numerous xanthomas typically occur in the skin, but are not usually painful unless at the site of recurrent contact/rubbing. Suprisingly, there is no increased risk of atherosclerosis or heart attacks.
Calling your health care provider
Call for an appointment with your health care provider (for screening) if lipoprotein lipase deficiency has been diagnosed in a member of your family or if you have extremely elevated triglyceride levels. Genetic counseling is recommended for anyone with a family history of this disease.
Prevention
There is no known prevention for this rare inherited disorder. Awareness of risks may allow early detection. Prompt institution of a very low fat diet can dramatically improve the symptoms of this disease.