The authors present the case-history of a 3-month old patient with severe hypertriacylglycerolaemia and hypercholesterolaemia, where the laboratory parameters improved after mother’s breast milk was substituted for donor’s milk, later for formula. With regard to the mentioned baseline laboratory finding which is typical for hyperlipoproteinaemia type III (dysbetalipoproteinaemia), the authors examined in the patient apo E polymorphism. They found phenotype E4/2 which is rare in the population and implies the presence of a mutant form of apolipoprotein E, responsible for an abnormal catabolism of lipoprotein plasma particles. To the manifestation of the disorder at the patient’s age contributed probably as so far undefined factor in human milk.

        Key words: hypertriacylglycerolaemia, hypercholesterolaemia, dysbetalipoproteinaemia, apolipoprotein E, breastfeeding