Triglycerides are fatty molecules serving as fuel for cells of the body. Dietary fat taken up by the intestines is transported in the form of triglycerides by large lipoproteins called chylomicrons. When chylomicrons are released in the blood stream, an activating protein in chylomicrons called apolipoprotein C2 is recognized by an enzyme (lipoprotein lipase or LPL) involved in triglycerides break down. The resulting components (fatty acids and glycerol) are taken up by cells to be stored (adipose tissue) or burned (muscle, heart). When LPL is deficient, chylomicrons accumulate in plasma, inducing massive hypertriglyceridemia reaching 10 to 100 folds the normal levels, particularly after a fat-rich meal. Genetic mutations on both parental chromosomes of either LPL or the activating protein C2 are responsible for familial chylomicronemia. Levels of triglycerides are high at birth particularly after meals. They cause abdominal pain, which can be the first alert to the onset of acute pancreatitis, a life threatening complication. Diagnosis is ascertained by a decrease of plasma LPL activity below 20% of normal, and the presence of genetic mutations on the LPL or apo C2 genes. This autosomal recessive disorder does not affect heterozygous relatives, although they have an increased susceptibility to combined hyperlipidemia (type IIb) associated with decreased plasma HDL cholesterol. They may be more susceptible to atherosclerosis than non-carriers, particularly if they gain in body weight or remain on a high fat diet. Patients with familial chylomicronemia must follow a lifetime diet extremely reduced in fat intake (<10% of total daily intake in calories). Approximately 1/1,000,000 people are affected in populations.
Last update: September 2000