The ultrastructure of the epidermis in psoriasis vulgaris as revealed by electron microscopy

The present electron microscopic study has been carried out on psoriatic skin from the upper arm, sacrum, and abdomen. The epidermal cells show rather even basal surfaces. The usually simple basement membrane may split up. Breaks in the membrane seem to occur. The reticular filaments are reduced in number. Between the collagen filaments is seen a fibrillar substance consisting of very fine filaments. Stratum basale comprises one layer of columnar cells. Occasionally two or three layers can be found. As to shape, orientation, and size, the cells occasionally show irregularities. The intercellular space is dilated. The cell surfaces are fairly even. Microvilli and desmosomes usually occur sparsely. A different type of attachment zone has been described. The plasma membranes show an asymmetric triple-layered pattern. In the nuclei components with concentrically arranged membranes are seen. Characteristic features are an over-all reduction in the formation of tonofibrillar material, a defective anastomosis and aggregation of the tonofibrils into larger bundles, and a poorly developed fibrillar delimitation of the perinuclear zones. The tonofilaments have a diameter of 50 ± 14 and are mainly arranged in fibrils. Mitochondria and α-cytomembranes are abundant. Numerous small, opaque particles are seen. Areas with a reticular pattern consisting of opaque dots connected by less opaque bridges are found in the epidermal cells and melanocytes. Melanocytes often occur in stratum basale, but no melanin pigment granules are seen in the epidermal cells.