Melanosis (haemosiderosis) ilei.

We report here a case of melanosis ilei where grossly visible greyish black pigmentation of the ileal mucosa was discovered at autopsy. Light microscopy showed Prussian blue positive pigment granules in macrophages in the lamina propria forming the core of villi. Ultrastructural examination showed that the pigment granules had the morphology of siderosomes which are known to be the electron microscopic equivalent of the haemosiderin granules seen with the light microscope. We know of no previous report where pigmentation of the ileal mucosa was ascribed to the presence of haemosiderin.