A mutation in the human lipoprotein lipase gene as the most common cause of familial chylomicronemia in French Canadians

Article Abstract:

Inherited chylomicronemia is a condition in which patients have abnormally high blood levels of certain fats, and develop abdominal pain, pancreatic inflammation, and fatty tumors in childhood. Other disorders related to high fat levels, such as premature atherosclerosis (deposition of fatty plaques on the walls of arteries), often develop in adulthood. Inherited chylomicronemia is usually the result of a genetically transmitted defect in lipoprotein lipase, an enzyme that clears chylomicrons (very small fat particles resulting from digestion) from the circulation, and regulates levels of very low-density lipoproteins (one class of fat-protein complex). Several DNA mutations have been identified that cause lipoprotein lipase deficiency, but consistent mutation patterns have not been found in different families and population subgroups. The current study found a particular mutation in 37 unrelated French Canadians with lipoprotein lipase deficiency. The mutation, which resulted in an abnormal amino acid sequence (leucine was substituted for proline) in the enzyme, was present in 73 percent of the mutant forms of the gene. Its frequency in this group was determined by means of the polymerase chain reaction, a method whereby selected segments of DNA can be amplified (replicated) for analysis. The lipoprotein lipase produced by the mutated gene was unable to catalyze (facilitate) biochemical reactions. Only one mutation of the sort described was found when 34 unrelated patients of non-French Canadian ancestry were similarly examined. French Canadians have the highest reported rate of lipoprotein lipase deficiency in the world, with a carrier rate of 1/40 in some parts of Quebec. A discussion is presented of the ways the aberrant gene might have been introduced into the gene pool in this region. Identification of this mutation will allow more accurate determination of the number of people who are carriers. (Consumer Summary produced by Reliance Medical Information, Inc.)

Canada, Physiological aspects, Demographic aspects, Diseases, Lipoprotein lipase, French-Canadians, French speaking Canadians, Hyperlipoproteinemia, Chylomicrons

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Reye's syndrome: a reappraisal of diagnosis in 49 presumptive cases

Article Abstract:

Reye's syndrome is an acute deterioration of brain tissue and brain function accompanied by a fatty degeneration of the liver and other organs. The cause of the disease remains unknown, but the syndrome often follows a viral infection such as influenza (flu), and some research has implicated the use of aspirin in these cases. Several recent studies have suggested that the rate of aspirin use in children and the incidence of Reye's syndrome have declined during the period of 1980 to 1985. At face value these data appear to support a relationship of aspirin use and Reye's syndrome. However, diagnostic practices have changed in the years since Reye's was first described and it is possible that, armed with current medical knowledge, a re-examination of prior cases could result in a re-classification of cases previously diagnosed as Reye's syndrome. Forty-nine cases, in which the patient was discharged or died, diagnosed as Reye's syndrome at one medical center over a 17-year period were reviewed by three clinicians. In 42 of the 49 cases (86 percent) there was agreement in diagnosing the patient's problem. In the remaining cases discussion among the clinicians resulted in the assignment of a diagnosis. The original diagnosis of Reye's syndrome was ranked certain in 1 case, probable in 11, and unlikely or excluded in 36 cases. This suggests that the actual occurrence of Reye's syndrome has always been low in this institution, and that the apparent reduction in the incidence of Reye's syndrome may be an artifact of prior mistaken diagnoses, rather than a result of decreased use of aspirin in treating children with viral infections. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diagnosis, Causes of, Influenza, Aspirin, Brain diseases, Pediatric neurology, Reye syndrome

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Neurologic crises in hereditary tyrosinemia

Article Abstract:

Hereditary tyrosinemia is a genetic disorder in which the final step in the breakdown of the amino acid tyrosine is blocked. Although generally uncommon, it seems to occur with greater frequency in the province of Quebec. Tyrosinemia can cause liver failure, kidney dysfunction, and liver cancer. Although neurological problems have been mentioned in previously published research, this study of 48 children with hereditary tyrosinemia revealed that neurologic crisis are a common manifestation of this disease. The children were identified by screening at birth. Beginning at an average age of one year, 20 children experienced neurologic episodes requiring hospitalization on 104 occasions. Symptoms included abnormally increased muscle tone in extensor muscles combined with severe pain, vomiting and paralysis of the normal intestinal contractions, muscle weakness, and self-mutilation. Paralysis prevented eight children from breathing without mechanical ventilation; 14 of the 20 died. Despite the severity of the crises, most children regained normal function between crises, and no abnormal biochemical findings could be correlated with these episodes. The neuropathologic events resulting from tyrosinemia are thought to be related to those observed in abnormalities of porphyrin metabolism; succinylacetone, a metabolite of tyrosine in these patients, accumulates and inhibits normal porphyrin metabolism. (Consumer Summary produced by Reliance Medical Information, Inc.)

Tyrosine metabolism, Metabolism, Inborn errors of, Inborn errors of metabolism, Amino acid metabolism, Inborn errors of, Inborn errors of amino acid metabolism, Porphyria

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