Chylomicrons and the formation of foam cells in type I hyperlipoproteinemia. A morphologic study.

Light and electron microscopic study of aspirated bone marrow of a patient with type I hyperlipoproteinemia disclosed large, birefringent foam cells which develop from phagocytosis of chylomicrons by histiocytes. Chylomicrons are taken up, singly and in aggregates, by infoldings of the plasma membranes of histiocytes; these infoldings become phagocytic vacuoles within the cytoplasm. As chylomicrons are metabolized, the foam cells decrease in size, lose birefringence and develop autofluorescent, electron-dense deposits of ceroid.