Flegel originally described hyperkeratosis lenticularis perstans (HLP) in 1958 as red-brown papules with horny scales of irregular outline measuring 1-5 mm in diameter and up to 1 mm in depth. Lesions are located primarily on the dorsal feet and lower legs, with a decreasing likelihood of manifestation proximally. Most cases have been reported in Europe.
* Small, red-brown, hyperkeratotic, 1-5 mm papules on the lower extremities are the most frequent and characteristic presentation of HLP. * Involvement of the ear pinnae, arms, palms, soles, and the oral mucosa has been reported, although these reports are rare. Involvement of the trunk has been reported but remains an unusual variant. * Removal of the scale reveals a bright red base, often with pinpoint bleeding. * A localized unilateral variant has been reported. * The trunk tends to be spared; absence of axial lesions is characteristic.
To date, the causes of HLP are unknown. Some authors suggest that exposure to the sun may be involved.