In 4 siblings, of whom 2 had symptoms of Wilson’s disease, electron microscopy showed that the number and size of lysosomes in the enterocytes were increased compared with controls. Electron-dense aggregates, observed near the lysosomes in the 2 symptomatic patients and 1 other sibling, were shown, by means of a microanalytical method, to contain copper. These findings could suggest a possible role of the small intestine in Wilson’s dise