Hyperkeratosis lenticularis perstans (Flegel's disease): our experience and review of the literature.

Hyperkeratosis lenticularis perstans (HLP), or Flegel's disease (FD), is a rare disorder of keratinization first described in 1958 by Flegel. HLP is characterized by asymptomatic small papules distributed symmetrically on the dorsal feet and lower part of the legs. It typically presents in the fourth or fifth decade of life. FD has been reported more commonly in women, and little is known about the pathogenesis of this rare dermatosis. Histological examination is mandatory to confirm the diagnosis, and the characteristic features are: focal compact hyperkeratosis, thinned stratum malpighii, epidermal atrophy, and a dense, band-like lymphocytic infiltrate in the papillary dermis. The treatment of FD is challenging, and a fully effective standard therapy does not exist. We report four cases of HLP that have been diagnosed at the Dermatology Unit of IRCCS Ca' Granda Ospedale Maggiore Policlinico in Milan, Italy, and a literature review is enclosed.