Ultrastructure of inborm errors of keratinization. VII. Porokeratosis Mibelli and disseminated superficial actinic porokeratosis.

The cornoid lamella and the underlying epidermis were studied by electron microscopy on specimens biopsied from 2 patients with porokeratosis Mibelli and 1 patient with actinic porokeratosis. Findings on the two types of porokeratoses are essentially the same. The cornoid lamella was composed chiefly of extremely irregular dark cells and a few numbers of dyskeratotic cells. Both cells retained a nuclear remnant and many other degraded organelles. The epidermal cells just beneath the cornoid lamella simultaneously demonstrated productive and degenerative signs. Some of these epidermal cells underwent dyskeratosis and appeared as corps ronds-like bodies in the granular layer. Two contradictory phenomena should be attributed to the pathogenesis of cornoid lamella. In the cornoid lamella above the sweat pore microvilli-structures were found.