Lipomembranous polycystic osteodysplasia.

A case of lipomembranous polycystic osteodysplasia is presented. The clinical features were characterized by multiple cystic changes of the bones and progressive psychomotor retardation. Although the diagnosis of polyostotic fibrous dysplasia of bone was made first because of expanded tumorlike lesions in bones, pathology of bone and bone marrow confirmed the diagnosis of lipomembranous polycystic osteodysplasia. Light microscopy showed a great number of peculiar undulating membranous structures in the adipose tissue. With the electron microscope the membrane seemed to be composed of an accumulation of endoplasmic reticulum-like tubular profiles. They appear first, in close connection with fat droplets, within the mesenchymal cell.