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Hyperkeratosis follicular and parafollicular, penetrating the dermis: causes, symptoms, diagnosis, treatment
Last reviewed: 07.07.2025
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Follicular and parafollicular hyperkeratosis penetrating the dermis (syn.: Kyrle's disease) is a rare disease with an unspecified type of inheritance, clinically manifested by keratotic papules, 3-4 mm to 1 cm in size, rarely more, localized mainly on the extensor surfaces of the extremities. In the center of each element is a conical hyperkeratotic plug. A tendency to follicular (in the area of the funnels of hair follicles) location is characteristic. Papules can merge to form polycyclic or linear, often warty foci.
Cases of disease development during long-term treatment with D-penicillamine in patients with diabetes mellitus and renal failure are described.
Pathomorphology. Large hyperkeratotic plugs are found in the epidermal depressions and sometimes in the widened openings of hair follicles. In the area of the horny plug, there are parakeratotic cells and cellular detritus stained with hematoxylin and eosin. Under the horny plugs, the granular layer is well developed, with the exception of areas of parakeratosis. In places where the granular layer is absent, foci of vacuolated dyskeratotic cells are observed in fresh elements. In old elements, the epidermis is atrophic, keratotic masses penetrate into the dermis, where a granulomatous reaction with giant cells of foreign bodies occurs. Collagen fibers with dystrophic phenomena, the number of elastic fibers is increased.
Histogenesis. The presence of dyskeratotic and parakeratotic cells indicates disturbances in the keratinization process, which is expressed in rapid premature keratinization of cells, which can begin already in the lower rows of the spinous layer and involve the cells of the basal layer in the process.
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