Bone marrow lipofuscin.

Lipofuscins are commonly present in the macrophages of the marrow. In unstained preparations they may be confused with haemosiderin, but they are readily distinguished by fluorescence microscopy. In contrast to the belief that lipofuscins are a manifestation of senility, no age dependence has been demonstrated. Exceptionally large amounts have been found in illnesses accompanied by fever and leucocytosis, in keeping with the concept of their formation from insoluble remains of ingested cell fragments. It is probable that the ;sea-blue histiocytes', described in the literature, are macrophages laden with strikingly uniform granules of lipofuscin.