Genital porokeratosis: a rare entity.

Sir,

Porokeratosis is an uncommon disorder of keratinization, the etiology of which is unknown. Annular plaques having central atrophy and raised keratotic border with groove clinically and cornoid lamella microscopically are the classical features. Porokeratosis occurring on the genital areas is considered as a rare entity. We report a case of 34-yr-old married male who consulted out-patient department of dermatology for lesions on the penis and scrotum. These lesions were on his genitals since last 2 yrs but as they were asymptomatic, no medical opinion was sought by him. On enquiry, there was no history of genital ulcer or inguinal swelling, neither any history of sexual promiscuity. Family history was noncontributory.

On examination, there were annular plaques with central area of atrophy and raised border on the shaft of penis [Figure 1]. Similar lesions were also found on the scrotum [Figure 2]. No such lesions were seen on other body parts and systemic examination was normal. His blood investigations like serum venereal disease research laboratory test (VDRL) and Enzyme-linked immunosorbent assay (ELISA) for HIV were negative, fasting and post-prandial blood sugar levels were normal. Application of gentian violet over the lesion followed by removal with alcohol revealed retention of the gentian violet in the groove at the border [Figure 3]. Skin biopsy from the raised border showed a column of parakeratosis arising from the epidermis (cornoid lamella) with absent granular layer and dyskeratotic cells beneath the cornoid lamella [Figure 4]. Thus a diagnosis of porokeratosis limited to the genitalia was made.

Figure 1

Annular plaques with raised border and central atrophy on the penis

Figure 2

Annular plaque with elevated keratotic border on the scrotum (arrow)

Figure 3

Retention of the gentian violet in the groove (arrow)

Figure 4

Column of parakeratosis (cornoid lamella) invaginating the epidermis, decreased granular layer and dyskeratotic cells (H and E, ×400)

Porokeratosis is disorder of keratinization with autosomal dominant inheritance. However, sporadic cases occurring late in life have been reported. Five different forms of porokeratosis have been described i.e., classical plaque-type porokeratosis of Mibelli, disseminated superficial actinic porokeratosis, linear porokeratosis, porokeratosis palmaris et plantaris and punctate porokeratosis. Microscopically, a column of parakeratosis invaginating the epidermis known as cornoid lamella is characteristic finding. Decreased granular layer and dyskeratotic cells are often seen beneath the cornoid lamella.

Porokeratosis involving the genitalia can occur as part of generalized porokeratosis with genital involvement or as localized porokeratosis that is confined to the genital area. Porokeratosis confined to the genitalia (genital porokeratosis) is considered as an extremely rare entity. It is classified as classic or plaque-type porokeratosis of mibelli. Lesions of genital porokeratosis are usually asymptomatic, but occasionally may be pruritic. Most commonly, it has been described to occur on the scrotum, followed by penis. Adjacent areas like buttock, natal cleft, groins and thighs can also be involved.[1] Lesion on the glans penis can present as erosive balanitis. Porter, et al., has reported a case involving the external urethral meatus.[2] Very few cases of porokeratosis involving genitalia with or without involvement of adjacent areas have been reported in literature.[3]

Similar to non-genital cases of porokeratosis, genital porokeratosis also shows predilection for male sex. However, few cases of genital porokeratosis involving the vulva have been reported.[45]

Uncommon form of genital porokeratosis presenting as a hyperkeratotic verrucous plaque involving the vestibule, fourchette and adjacent perineal skin mimicking condyloma acuminata has been reported by Sengupta, et al.[5] Similarly, verrucous lesion on the scrotum[1] and lesion mimicking psoriasis on the buttock has been reported.[6]

Annular lichen planus can mimic lesions of porokeratosis. Similar to porokeratosis it is mostly asymptomatic and may have central hyperpigmentation/atrophy and raised border. However, meticulous clinical examination with magnifying lens, simple clinical test like application of dye like gentian violet and skin biopsy are useful to differentiate. Keratotic ridge with a central groove clinically and cornoid lamella with decreased granular layer histopathologically help differentiate porokeratosis from annular lichen planus.

Treatment modalities for genital porokeratosis are same as that of porokeratosis occurring on other sites. These include cryotherapy (liquid N2), surgical excision, CO2 laser ablation, topical 5% 5-fluorouracil, vit. D3 analogues, retinoids and imiquimod cream.[237] 3% diclofenac gel has been found to be useful for the symptomatic relief and stabilizing evolution of lesions of genital porokeratosis.[8]

Malignant degeneration has been reported in all forms of porokeratosis. Large lesions, lesions of long-standing duration, and the linear type of porokeratosis were found to be at greatest risk. But no such change has been reported till date, in lesions of genital porokeratosis.[9]