Porokeratotic eccrine ostial and dermal duct nevus: Case report of a rare entity.

A 47-year-old male patient presented with itchy skin lesions over his left foot. On examination, patient had multiple, grouped but discrete, pinhead to 0.5 mm sized, crusted, folliculopapular and comedone-like lesions over the left foot. Lesions were keratotic in feel, had crater-like margins and were arranged in a linear fashion on the left foot starting from dorsum of 3rd toe, margin of 4th toe, sole, lateral aspect and dorsum of the foot, extending up to the posterior aspect of the heel [Figure 1a–c]. Lesions were present since birth and patient had no complaints except occasional mild pruritus.

Figure 1

(a-c) Discrete, keratotic lesions on sole, toes and heel of foot in a linear distribution

Histopathology from the lesion on the side of the foot showed variable hyperkeratosis, acanthosis with parakeratotic invaginations in the epidermis. Dermis showed mature eccrine sweat glands in the mid and lower dermis underlying the porokeratotic column [Figure 2a and b]. Histopathological changes confirmed the clinical diagnosis of porokeratotic eccrine ostial and dermal duct nevus (PEODDN).

Figure 2

(a) Parakeratotic column with underlying eccrine sweat glands on histopathology (H and E, ×100). (b) Close-up view of parakeratotic column (H and E, ×400)

Porokeratotic eccrine ostial and dermal duct nevus is a rare congenital hamartoma with eccrine differentiation. Lesions of PEODDN present since birth or may appear during childhood or puberty. They are clinically characterized by asymptomatic, small, scaly, discrete, papules filled with keratin plugs resembling comedones arranged in a linear fashion on palms and/or soles.[1] The flexural aspect of hands and feet, and even trunk may be involved along lines of Blaschko. Extensive generalized involvement, either unilateral or systematized has also been described.[234] The lesions appear as comedones but at sites where there are no pilosebaceous follicles. The disorder is nonhereditary and may represent a genetic mosaicism.[5] PEODDN is histologically characterized by well-formed coronoid lamellae occurring in close proximity to underlying dilated eccrine ducts and acrosyringia.[6] A variety of therapies have been utilized to eradicate the lesions of PEODDN including topical keratolytic agents, systemic and topical retinoids, CO2 laser therapy etc.[67]

Our case of PEODDN is reported as the entity itself is very rare and very few cases have been reported in the literature till date, with only three cases from India.[8910]