Sir,

Porokeratosis of Mibelli is a clinical form of porokeratosis among an original set of dermatoses characterized by disorders of epidermal differentiation and keratinization. It represents one third of all cases of porokeratosis. Its etiology is not well established. It occurs most often in childhood or adolescence and predominantly in males. It is clinically characterized by one or more annular plaques with raised borders, atrophic centers, and a centrifugal evolution located on the extremities [1]. It has, recently, been reported that some cases of porokeratosis of Mibelli show a low frequency of hyperkeratotic lesions, which some authors have called the hyperkeratotic variant of porokeratosis Mibelli. Diagnostic confirmation is achieved through a histopathological examination with the finding of the cornoid lamella and hypogranulosis [2]. The hyperkeratotic variant is characterized by more severe hyperkeratosis with abundant coronal lamellae on histology. The usefulness of dermoscopy lies in the fact that it orientates the diagnosis by showing classically white, central areas without structures, dots and reddish-brown globules, and a peripheral border with a double margin translating the coronoid lamellae. Therapeutic management is based on keratolytic agents [2,3]. Herein, we present a clinical and dermoscopic description of the hyperkeratotic variant of porokeratosis of Mibelli.

A nineteen-year-old patient with a history of peripheral spondyloarthritis presented with slightly pruritic lesions on the back of the hand persistent for five years, treated as psoriasis with topical steroids with no improvement. A clinical examination revealed multiple, verrucous, slightly erythematous, and hyperkeratotic papules located on the back of the left hand (Fig. 1). Dermoscopy without immersion showed the predominance of whitish, verrucous areas without structures, white scales, after immersion: brown spots and globules and erythema (Fig. 2). A skin biopsy was performed showing a large predominance of coronoid lamellae consisting of parakeratotic cells in a “stack of plates” resting on a sudden depression of the epidermis without a granular layer at this level and a lichenoid reaction suggesting porokeratosis of Mibelli (Fig. 3). The case of our patient differed from the classical form characterized by a rather verrucous and hyperkeratotic aspect of the lesions. This observation is, therefore, closer to the hyperkeratotic form, which is rarer. A dermoscopic description of this entity has, to the best of our knowledge, not yet been reported.

	Figure 1: Multiple, verrucous, slightly erythematous, and hyperkeratotic papules located on the back of the left hand.
	Figure 2: Dermoscopic findings without immersion: whitish verrucous areas without structures (blue star), white scales (a) with immersion brown spots and globules (black arrow), erythema (b).
	Figure 3: Coronoid lamellae above an epidermal depression with agranulosis, vacuolation of the underlying epidermal cells, and a lichenoid reaction (H&E: G x 50 : 2).

Consent

REFERENCES

1. Jha AK, Sonthalia S, Lallas A. Dermoscopy of porokeratosis of Mibelli. Indian Dermatol Online J. 2017;8:304-5.

2. Ferreira FR, Santos LD, Tagliarini FA, Lira ML. Porokeratosis of Mibelli–Literature review and a case report. An Bras Dermatol. 2013;88(6 Suppl 1):179-82.

3. Mrabat S, Baybay H, Oujdi S, Douhi Z, Elloudi S, Mernissi FZ. Porokeratosis:A diagnosis made easy by the dermoscope!Our Dermatol Online. 2020;11:e141.1.