An ultrastructural study of the epidermis in hyperkeratosis lenticularis perstans

A 60-year-old Japanese man contracted hyperkeratosis lenticularis perstans (Flegel). Biopsy specimens of the keratotic papules on the dorsa of the feet were studied with electron microscopy. An increase in the number of membrane coating granules, keratohyalin granules and tonofilaments was the most prominent feature of the keratinocytes underlying the keratotic papule. However, in the area just above the cone-shaped dermal infiltration, membrane coating granules were absent and keratohyalin granules and tonofilaments were poorly developed.