Myospherulosis has recently been shown to be composed of altered erythrocytes. Mysopherules have been produced in vivo and in vitro using a petrolatum-based tetracycline antibiotic ointment (Achromycin). In the reported study, myospherules were produced in vitro using either lanolin or petrolatum, the two components of the vehicle of this ointment. Additionally, human fat produced myospherules in vitro.