Ultrastructure of the haemophilic synovial membrane and electron-probe X-ray analysis of haemosiderin.

An ultrastructural study of the haemophilic synovial membrane revealed the presence of solitary siderosomes, compound siderosomes and a peppering of the cell cytoplasm with electron-dense particles. These changes were found in synovial intimal cells, subsynovial macrophages and fibroblasts. Electron-probe X-ray analysis of siderosomes revealed the presence of iron and traces of phosphorus. On the basis of previous and present studies it is postulated that haemosiderin is essentially a condensate of hydrated ferric oxide and that a variable amount of phospholipid material lies in company with it in the siderosome.