Congenital unilateral reticulate keratotic papules on the lower extremity

Abstract

A boy in his late teens presented with asymptomatic browncolored raised lesions over the right leg since birth. Lesions gradually increased in size and number over a period of a few years, and there were no lesions elsewhere. Family history was noncontributory. There was no history of any preceding skin eruption either at the time of birth or at any point thereafter.Examination showed multiple grouped dark brown follicular hyperkeratotic papules coalescing at the center to form plaque over and slightly above the medial aspect of the right knee with a few scattered follicular lesions over the adjoining thigh and leg. Plaque showed linear and reticulate configuration especially at the borders. Majority of the lesions had a central keratotic plug with few showing pits as remnants of fallen plugs (Fig. 1).The rest of the mucocutaneous examination was within normal limits. Histopathological findingsThe findings revealed marked hyperkeratosis over a prominent follicular plug causing a cup-like depression in the center of an essentially normal epidermis (Fig. 2a). The epidermis beneath this plug showed cytoplasmic vacuolization with a thin rim of cytoplasm in perinuclear location. The granular layer in this portion had coarse keratohyalin and trichohyalin granules (Fig. 2b). The vacuolar change spared the basal layer and sharply corresponded to the extent of the overlying hyperkeratosis.The patient was started on tretinoin 0.05% cream once daily which caused visible flattening of lesions after 4 weeks. Figure 1 Multiple grouped dark brown follicular hyperkeratotic papules with a central keratotic plug over the medial aspect of the right knee ª