Electron-microscopic changes in xerosis senilis epidermis. Its abnormal membrane-coating granule formation.

Skin specimens of patients with xerosis senilis were examined electron microscopically. The changes were as follows: (1) The electron density of the stratum corneum was uniformly low and no keratin pattern was observed in the lowermost cells of the stratum corneum. (2) The number of keratohyalin granules was decreased but their electron density was normal. (3) There were no lamellate membrane-coating granules formed in the cells of the stratum granulosum and there were many small vesicles which were similar in size and shape to membrane-coating granules, but lacked a lamellate internal structure. This abnormal vesicle formation occurred in the epidermis of the same xerosis senilis patients both in winter and summer. This observation indicates that the change in the formation of membrane-coating granules could be an age-dependent disorder of the differentiation of keratinocytes. (4) Being accompanied by an age-related reduction in lipid production, the deficient formation of membrane-coating granules leads to the disappearance of the lipid film which surrounds the stratum corneum cells. This and the reduction in the surface lipid originating in the sebaceous glands could result in an increase in transepidermal water loss leading to the asteatotic scaly stratum corneum seen in the skin of patients with xerosis senilis in winter.