PMC4772611_01
a Lateral view of the right leg, showing multiple small red-brown papules 1-3 mm in size with a central keratotic plug. b Close-up view of the area displayed in a, showing many typical lesions at different stages of development. A hair can be seen protruding out of some of the follicular (F) lesions but not out of the parafollicular (PF) lesions. c Histology of the lesion, showing the keratinous plug (1) filling the epidermal invagination (EI). Parakeratosis (2) and basophilic debris (3) can be seen within the plug. There is a dense inflammatory infiltrate (4) in the upper dermis.
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F1
A 6-year-old Yemeni girl presented with a 2-year history of generalized asymptomatic papules with a central lentiform keratinous plug (fig. 1). The patient exhibited the clinical characteristics of FD; i.e., generalized small lesions (1-5 mm, fig. 1a) mainly over the face, trunk, and extensor surfaces of the extremities, rather than the large lesions typically observed in KD (5-15 mm). Closer examination revealed that the lesions were at different stages of development, namely follicular or parafollicular (fig. 1b). Lesions without a hair were generally dome-shaped, brown-red papules with a central black keratinous plug surrounded by a whitish scale (fig. 1b). Histological analysis of a skin punch biopsy from the right leg revealed characteristics more consistent with KD than FD: epidermal invagination of orthokeratotic and parakeratotic central plugs containing basophilic debris (fig. 1c). On the other hand, the patient also exhibited the shallow, nonpenetrating central plugs typical of FD, rather than the large, deep penetrating plugs typical of KD (fig 1c).