Exclusive Facial Actinic Porokeratosis.

Two healthy siblings aged 16 years and 13 years born out of consanguineous marriage presented with complaints of lesions over the face of 5 years and 3 years duration, respectively. The lesions initially started as a small black dot on the nose and then gradually increased in number and size to involve the paranasal area and the cheeks [Figures 1 and 2]. There was history of pruritus on exposure to sunlight. No other parts of the body were affected. None of the family members gave history of similar complaints. On examination, multiple tan colored flat topped macules to plaques of varying sizes with a thready border were seen on the nose, cheeks, and eyelids. Dermoscopic examination done using a Dermlite DL1 dermoscope with 15× magnification showed a flat center showing dots and globules with a white double marginated keratotic border that represents the coronoid lamella [Figure 3a and b]. They were clinically diagnosed to have porokeratosis (PK). Biopsy done from the lesion on the face showed stratified squamous epithelium with focal keratin filled invagination. Dermis showed melanin clumps and dense lymphocytic infiltrate. The features were all consistent with actinic PK [Figure 4].

Figure 1

Porokeratotic lesions on the nose and left infraorbital region of the older patient

Figure 2

Porokeratotic lesions seen over the nose and cheek in the younger patient

Figure 3

Well-demarcated lesions showing a skin colored central part with a hyperpigmented border on dermoscopy (a) (black arrow) (non-polarized mode) and white coronoid lamella seen as double track and dark brown dots and globules in the center seen on dermoscopy (b) (white arrow) (polarized mode)

Figure 4

Histopathology features from the peripheral raised edge showing the coronoid lamella with parakeratotic cells in focal keratin filled invagination and the absent granular layer beneath it with lymphocytic infiltrate (H and E, ×10)

Both the patients were prescribed topical sunscreen during the day and 0.025% Tretinoin to be applied at bed time.

PK first described by Mibelli in 1893 includes a heterogeneous group of disorders of epidermal keratinization characterized by annular plaques with an atrophic center and hyperkeratotic edges, histologically showing coronoid lamella. Several types have been documented.[1] Exclusive facial PK that is a rare entity was described by Nabai and Mehregan in 1979.[2] It typically presents as single to multiple plaques on the distal part of the nose ranging from 0.1 cm to several centimeters in size surrounded by a keratotic rim.[3]

On dermoscopy, all variants of PK reveal a well-defined, whitish yellow peripheral annular structure, with a brownish pigmentation in the inner side also described as “the outlines of a volcanic crater as observed from a high point.”[45] Typically, the central area is seen as dots and globules, and the border that is the coronoid lamella has been described as diamond necklace or white track.[6]

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Conflicts of interest

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