Type I hyperlipoproteinemia

Alternative names
Familial lipoprotein lipase deficiencye; Familial chylomicronemia

Definition
Familial lipoprotein lipase deficiency is 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.

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 a high level of chylomicrons, a lipoprotein that carries fats from digested food into the blood stream. The chylomicrons are not broken down properly because of the deficiency of the lipoprotein lipase enzyme. This results in a build up of fat-laden chylomicrons in blood. 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, multiple unexplained episodes of pancreatitis, and failure to thrive in infancy. The incidence is 1 out of 1,000,000 people. The disease usually shows up in infancy or early childhood.

Symptoms

     
  • Abdominal pain (may manifest as colic in infancy)  
  • Nausea, vomiting, loss of appetite  
  • Failure to thrive in infancy  
  • Musculoskeletal pain  
  • Skin lesions - xanthomas (fatty deposits in the skin)

Signs and tests
A physical examination may reveal xanthomas, an enlarged liver, an enlarged spleen, and jaundice. An eye examination reveals pale retinas and whitish retinal vessels.

Tests or observations that may indicate this disorder is present include:

     
  • Milky appearing serum or plasma from blood  
  • A special test showing little or no lipoprotein lipase activity in blood collected after treatment with intravenous heparin  
  • High 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 blood serum taken after fasting  
  • A test for apolipoprotein CII deficiency, which may cause a rare subset of this disease in people with normal lipoprotein lipase activity  
  • Genetic testing, which may reveal a mutation in the genes for lipoprotein lipase or apolipoprotein CII

Treatment

Treatment is intended to control the symptoms and blood triglyceride levels with a very low fat diet. Fat intake usually must be less than 20 grams per day to keep the symptoms from coming back.

Twenty grams of fat is equivalent to one of the following:

     
  • two 8-ounce glasses of whole milk  
  • 4 teaspoons of margarine  
  • 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 supplements are recommended. Dietary counseling can be helpful for patients trying to stick to a strict diet and maintain adequate calorie and nutrient intake. Pancreatitis responds to conventional treatments for that disorder.

Expectations (prognosis)
By following a very low-fat diet, a person may 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 rubbing. Surprisingly, there is no increased risk of atherosclerosis or heart attacks.

Calling your health care provider
Call your health care provider for screening if lipoprotein lipase deficiency has been diagnosed in a family member 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.

Johns Hopkins patient information

Last revised: December 4, 2012
by Harutyun Medina, M.D.

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