Membranous lipodystrophy. Light and electron microscopic study of a biopsy case.

Membranous lipodystrophy is a peculiar systemic disease almost exclusively found in Japan and Scandinavia and characterized by formation of numerous membranous structures in the adipose tissue of bone marrow and soft tissue. Light and electron microscopic study of a biopsy case of the disease was presented. The membranous structures consisted of membrane and inner space on both light and electron microscopic study. The membrane consisted of two kinds of layers, dense and amorphous. The dense layer was positive for lipid stainings. The amorphous layer did not show any definite lipid constituents and was supposed to consist of an amorphous substance derived from abnormal fat metabolism of diseased fat cells, degenerative cytoplasms of the diseased cells, and/or stromal cells. It probably also had some stromal substance alteration due to membranolipodystrophic change. Accumulation of the amorphous layer in the interstitium leads to degeneration and disappearance of adjacent fat cells. This process may play a role in further advance of membranous structures.