sQUIZ your knowledge! Linear keratotic plaques over the forearm
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A 47-year-old otherwise healthy female presented with mildly pruritic elevated skin eruptions restricted to her left upper limb, which she had had for the preceding two decades. The lesion initially developed as a small horny
bump over the hand and gradually progressed over the next two years to its present size and extent. The condition was stable henceforth. Clinical examination revealed multiple skin-coloured to brownish discrete keratotic and pitted papules, coalescing into plaques, arranged linearly over the lateral border of the left upper limb, involving the dorsum of the hand and forearm up to the mid-arm (figure 1A). Skin biopsy from a representative lesion, followed by histopathological examination, showed hyperkeratosis, acanthosis, and parakeratotic invaginations in the epidermis with focal hypogranulosis; acrosyringeal ducts in the upper dermis were shown to underly the cornoid lamellae (figure 1B, C). What is your diagnosis?
A
B
C
Figure 1. A) Linearly distributed keratotic and pitted papules, coalescing into plaques, over the left upper limb. B, C) Histopathology showing hyperkeratosis, acanthosis, and parakeratotic invaginations into the epidermis with focal hypogranulosis; acrosyringeal ducts in the upper dermis underly the cornoid lamellae (H&E, x40 in [B] and x100 in [C]).
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EJD, vol. 30, n◦ 4, July-August 2020
Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) Ablative CO2 laser therapy led to significant flattening of lesions within a month. No recurrence was noted on followup after six months. PEODDN, first reported as a “comedo nevus of the palm” by Marsden et al. in 1979, is a rare benign nevoid disorder that presents at birth, during childhood or puberty [1]. PEODDN is considered to be a mosaic form of keratitis ichthyosis deafness syndrome, caused by somatic mutation in GJB2 which encodes for gap junction protein connexin-26 [2]. The new proposed term “porokeratotic adnexal ostial nevus (PAON)” essentially encompasses the two described entities: PEODDN and porokeratotic eccrine and hair follicle nevus [1]. Clinically, it manifests as comedo-like palmoplantar lesions or multiple punctate and keratotic papules and plaques that usually follow a linear distribution along Blaschko’s lines; rarely, lesions may be more widespread [3]. Conditions associated with PEODDN include hyperthyroidism, sensory polyneuropathy, deafness, developmental delay, seizure disorder, hemiparesis, breast hypoplasia, scoliosis, alopecia, onychodysplasia, Bowen’s disease and squamous cell carcinoma [4]. PEODDN must be differentiated clinically from nevus comedonicus, linear verrucous epidermal nevus, inflammatory linear verrucous epidermal nevus (ILVEN), linear psoriasis, linear porokeratosis, dilated pore nevus, linear lichen planus, punctate palmoplantar keratoderma, and punctate porokeratosis. Characteristic histopathological features of PEODDN include orthokeratosis with a parakeratotic column occupying an invagination of the epidermis; the base of the column shows loss of granular cells. The para
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