Peliosis-like ultrastructural changes of the hepatic sinusoids in human chronic hypervitaminosis A: report of three cases.

In addition to hypertrophy of Ito cells and perisinusoidal fibrosis, previously unrecognized ultrastructural abnormalities of the hepatic sinusoids were observed in three patients with chronic hypervitaminosis A: 1) large areas of communication between the sinusoidal lumina and the perisinusoidal spaces, allowing extravasation of blood cells; 2) marked dilation of the perisinusoidal spaces; and 3) swelling and clarification of endothelial cells. Most of these changes, along with some other sinusoidal barrier alterations previously reported in chronic hypervitaminosis A (i.e., bleb formation on the sinusoidal membrane of the hepatocytes and the presence of multiple cellular layers lining the sinusoids), are strikingly similar to those observed in peliosis hepatis. The present findings suggest that sinusoidal barrier abnormalities might constitute a major event in the pathophysiology of vitamin A-induced liver injury as well as of peliosis hepatis.