Phenotypic variation of mutations in the human lipoprotein-lipase gene.

We have described a large number of different mutations in the LPL gene that result in completely catalytically defective LPL protein. More recently exonic polymorphisms in the LPL gene have been described that do not result in the catalytic activity of LPL being significantly impaired. Furthermore we have recently described a patient who is homozygous for a mutation in the LPL gene in a conserved region of exon 5 that results only in partial residual activity and a very mild clinical phenotype. This may suggest that the frequency of mutations in the LPL gene is greater than has been previously recognized. Recognition and selection of patients for analysis was based on the phenotype of chylomicronaemia. However, the existence of the Ser172-Cys mutation in the LPL gene that results in only moderate hypertriglyceridaemia in the absence of environmental factors might suggest that mutations in this gene are more frequent and could be seen in patients with a milder clinical phenotype. The clue to detecting these changes in the LPL gene might be to investigate patients who present with chylomicronaemia due to different environmental triggers while, in the absence of these environmental factors, they have only moderate hypertriglyceridaemia.