Lipoprotein lipase Deficiency (LPL Def.) Is a rare autosomal recessive disorder that affects about one in million children in Europe and North America. However, the prevalence is higher among Jews and Arabs because of consanguineous marriages. LPL Enzyme is found in the gut, striated muscles and adipose tissue. LPL deficiency results from mutations in the LPL gene. Over 30 mutations have been reported so far. These include insertion-deletions mutations, splice-site defects and nonsense mutations, particularly in the highly conserved exons of the gene (4,5 and 6). Presents early in life with abdominal colic, with or without eruptive xanthomas, paralytic ileus and hepatosplenomegaly. Lipemia retinalis is usually present, but premature atherosclerosis is uncommon. Acute pancreatitis and peritonitis are life-threatening complications. The plasma is creamy with profound hypertriglyceridemia (4000-10000 mg/dl i.e. 45.6-114 mmol/l) plus hypercholesterolemia (usually one-tenth of triglycerides level). The elevated chylomicrons replaces water in plasma producing artificial decrease in plasma electrolyte particularly sodium (spurious hyponatremia). For each 1000 mg/dl increase of TG serum sodium level drops between 2-4 mmol/l. Diagnosis is easy with the creamy plasma and elevated TG, but confirmation of the etiology is by assessing the LPL enzyme activity (post heparin lipolytic activity test), which is usually absent or markedly reduced. Two phenotypes are recognized : type-I where only chylomicrons are elevated and type-V where both chylomicrons and VLDL are elevated. Parents of LPL deficient patients often have LPL activity halfway between normal controls and patients and most of them showed elevated fasting TG levels. Treatment is a diet very low in fat (10-15% of total calorie intake). Fat constitutes 40% of total calorie of breast milk. Affected infants should be given Portagen, a soybean-based formula containing medium-chain TG (MCT). MCT do not require the formation of chylomicrons for absorption, since they are directly transported from the intestine to the liver by the portal vein. MCT rich oils e.g. coconut oil (66% of it is MCT) should be given to all patients together with Portagen or alone when the special formula is not available. Some patients may benefit from therapy with omega 3 fatty acids and cod liver oil. Care must be taken that affected infants get at least 1% of their calories from the essential fatty acid linoleic acid. Triglycerides lowering medications (fibrates and nicotinic acid) are ineffective and should not be given. However, some experts recommend use of small dose of statins if the blood cholesterol is >400 mg/dl. Genetic counseling should be offered to parents. Professor Abdelaziz Elamin (University of Khartoum)
Posted on: Thu, 17 Oct 2013 21:05:39 +0000