Background
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. [1] 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.
Pathophysiology
No instigating factor has been identified clearly; some investigators have implicated UV light. However, in one case report, evidence of Borrelia infection (Borrelia burgdorferi and Borrelia garinii) was found using DNA sequencing in fresh tissue and blood from a patient with hyperkeratosis lenticularis perstans, without clinical evidence of Lyme borreliosis. [2] Ultrastructurally, a loss or decreased number of membrane-coating granules (also termed Odland bodies) has been reported. Membrane-coating granules are influential in the normal process of desquamation. A decrease, malformation, or absence of these membrane-coating granules may result in decreased desquamation of the stratum corneum, retention hyperkeratosis, and clinically keratotic hyperkeratosis lenticularis perstans lesions. Some authors have suggested that a cell-mediated cytotoxicity against epithelial cells may be involved in the pathogenesis of hyperkeratosis lenticularis perstans.
Epidemiology
Frequency
United States
No data exist on incidence or prevalence of this disease. Hyperkeratosis lenticularis perstans (Flegel disease) likely has both a familial and nonfamilial variant, since several reports have postulated both an autosomal dominant and a sporadic mode of inheritance. [3]
International
Most cases have been reported in Europe. International incidence is similar to that seen in the United States.
Race
Hyperkeratosis lenticularis perstans does not have a race predilection, although it has mostly been reported in the white population.
Sex
No sex predilection is apparent.
Age
Hyperkeratosis lenticularis perstans reportedly occurs most commonly in mid-to-older age groups; however, reports exist of hyperkeratosis lenticularis perstans occurring in patients as young as 13 years.
Prognosis
Except for the possibility that lesions may progress slowly and involve more proximal sites, prognosis for hyperkeratosis lenticularis perstans (Flegel disease) is excellent. No mortality has been reported.
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Clinical photograph of the upper thigh showing numerous red-brown papules with sparing of the inguinal crease.
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A higher-powered view of the patient seen in the previous image. Photograph of the upper thigh demonstrates 1- to 4-mm, noncoalescing keratotic papules.
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Hematoxylin and eosin-stained section, low magnification. Epidermal hyperplasia with rete elongation surmounted by a thickened, compact, hyperkeratotic scale. A bandlike lymphoid infiltrate expands the papillary dermis.
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Hematoxylin and eosin-stained section, medium magnification. The lateral edge of the lesion demonstrates abrupt hyperkeratosis and a combination of epidermal atrophy and acanthosis.
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Hematoxylin and eosin-stained section, high magnification. The section shows mostly orthokeratotic scale, thinning of the epidermis with a diminished granular cell layer, and an infiltrate of lymphocytes in the superficial dermis, which approximate the dermal-epidermal interface.
