Also known as: Lipoprotein lipase and apo C-II deficiencies
Triglycerides (TGs) are the main form of fat present in the diet and are a substantial source of energy for daily activity. TGs from the gut are transported in the blood as chylomicrons, which are complex fat globules also containing cholesterol and protein, including the protein apo C-II. An enzyme called lipoprotein lipase, found on the wall of blood vessels, removes the TGs from chylomicrons, to be used by muscle or fat cells. TGs also travel in the blood within very-low-density lipoproteins (VLDL) which are similar to chylomicrons. VLDL carries fat made in the liver to the tissues such as muscle and fat.
Hypertriglyceridaemia occurs when there is too much triglyceride in the blood, but the cholesterol level is normal or only slightly elevated.
Medical text written September 2014, by Dr M Sharrard, Consultant Paediatrician with Special Interest in Metabolic disease, Sheffield Children’s Hospital, Sheffield, UK.
The most serious complication of hypertriglyceridaemia is acute pancreatitis. This occurs when the pancreas becomes inflamed and releases digestive enzymes into the abdomen causing damage. Pancreatitis causes very severe abdominal pain and can be life-threatening.
Many people with hypertriglyceridaemia experience abdominal pain because of long term inflammation of the pancreas. The liver and spleen may be enlarged and there may be fatty lumps in the skin (called eruptive xanthomas) often round the elbows and knees.
Hypertriglyceridaemia with excessive chylomicrons in the blood is usually a genetic disease. There may be an inherited deficiency of the enzyme lipoprotein lipase caused by mutation in the LPL gene, or more rarely of the protein apo C-II caused by mutations in the APOC2 gene. These disorders are very rare, affecting about 1 in every one million people in the UK, although more people from Asia are affected.
Hypertriglyceridaemia is diagnosed by a blood test to measure triglyceride levels. Special blood tests can be used to measure lipoprotein lipase and apo C-II levels, or genetic testing may be used to find the gene defect.
Some children are diagnosed when they have a blood tests and their blood plasma looks abnormally creamy.
Treatment is aimed at lowering blood triglycerides to a safe level. A very low fat diet is the main part of treatment. This should be supervised by an experienced dietician. Special fats called medium chain triglycerides (MCT) can be used in infant formulas or as dietary supplements to provide energy and MCT may help to reduce triglyceride levels. Fat soluble vitamins and essential fatty acids (often as walnut oil) should be given as supplements.
Lipoprotein lipase and apo C-II deficiencies are recessively inherited – both parents carry one copy of a mutant LPL or APOC2 gene, and the affected child inherits the mutated gene from each unaffected carrier parent.
Prenatal diagnosis is possible if the gene mutation is known, although it is rarely requested as effective treatment is available.
Information and support in the UK for organic acidaemias is provided by Metabolic Support UK (see entry Inherited Metabolic diseases).