JOSEF KYRLE1 described in 1916, from Finger's clinic in Vienna, the first reported instance of a disease to which he gave the name hyperkeratosis follicularis et parafollicularis in cutem penetrans. The patient was a 22 year old woman with an eruption of eight months' duration, characterized by polycyclic hyperkeratotic plaques in the axillas,. on the forearms and on the shoulders. On removal of the heavy scale and crust, the plaques were seen to be composed of closely set, discrete, crateriform papules a few millimeters in diameter, topped by a central depression about 2 mm. in width and depth. Microscopically, the floors of these depressions were seen to be formed by the bases of keratinous conical pegs, the points of which extended downward through the acanthotic epidermis and, in some of the papules, actually penetrated through the basal layer and entered the corium, where they excited a typical foreign body
ARNOLD HL. HYPERKERATOSIS PENETRANS: Report of a Case of a Probable Variant of Kyrle's Disease. Arch Derm Syphilol. 1947;55(5):633–638. doi:10.1001/archderm.1947.01520050035004
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