The spleen in type I hyperlipoproteinemia. Histochemical, biochemical, microfluorometric and electron microscopic observations.

Histochemical, biochemical, microfluorometric and electron microscopic studies were made of the spleen of a patient with type I hyperlipoproteinemia. Foam cells were observed that contained a material identified as ceroid on the basis of its autofluorescence, acid-fastness, sudanophilia, PAS-positivity and insolubility in organic solvents. Electron microscopy showed that the ceroid was organized in the form of granules with concentric lamellae of irregular periodicity. The process of formation of these granules is described in detail. The ceroid was considered to represent nondigestible end products of the metabolism of chylomicrons taken up by macrophages in splenic sinusoids.