Porokeratosis of Mibelli in an HIV-positive patient*

Porokeratosis represents a group of disorders of epidermal keratinization that are characterized by one or more annular plaques surrounded by a histologically distinctive hyperkeratotic ridge-like border called the cornoid lamella. Many studies showed that organ transplantation and immunosuppression were associated in a significant number of cases. Furthermore, an association with squamous cell carcinoma and basal cell carcinoma has been noted in all variants of porokeratosis. The rarity of this disorder and its atypical clinical presentation – a single lesion on the thumb of an HIV-positive male patient – motivated this report.


INTRODUCTION
Porokeratosis (PK) is a group of abnormal keratinization in the epidermis. 1 It is a chronic and often hereditary (autosomal dominant) disorder. However, most cases appear to be sporadic.
Lesions are characterized by annular keratotic papules or plaques with raised peripheral ridges that spread centrifugally. It was first described in 1893 by Mibelli. [2][3][4][5] It is usually asymptomatic, but pruritus may occur. 2,3 PK variants are associated, and more than one type may develop in a patient. Localized forms include PK of Mibelli (PM), linear PK and punctate PK. Disseminated forms include superficial, actinic superficial, and palmoplantar PK. [1][2][3][4][5] Lesions may occur in any part of the body including the mucous membranes, but extremities are the most affected sites.
Multiple lesions may occur, but are usually unilateral and regionally located.
The etiology of PK is multifactorial and includes genetic factors, ultraviolet radiation, trauma, and infectious agents. 1 Cases associated with organ transplantation, hematologic malignancies, HIV infection, use of immunosuppressant drugs, and chemotherapy have been reported. 2,3,4 Some reports suggest a relationship between the lesion evolution and the degree of immunosuppression. 1,6,7 Clinical and molecular evidence has shown that PK can be considered a premalignant condition. 8 The rarity of this disorder and its atypical clinical presentation -a single lesion on the thumb of an HIV-positive patient -motivated this report.

CASE REPORT
We report a white 34-year-old male patient referred to our institution with a one-year lesion on the right first digit. The lesion appeared as an erythematous papule, which markedly progressed in the last six months. The patient reported local pain and bleeding af-

DISCUSSION
PM is a rare entity. Lesion may appear at any age, but are most common during childhood, especially when inherited. The disease has predilection for males. [2][3][4][5]  The identification of a cornoid lamella is characteristic and essential for the histopathological diagnosis of PK. It corresponds     Late sporadic cases have been linked to drugs, such as thiazide diuretics, and biologics, such as etanercept in patients with psoriasis. 2 The latency period between the onset of immunosuppressive therapy and the appearance of PK ranged from 1 week to 16 years. 3 Malignant degeneration has been reported in all forms of PK with a 7.5-11% incidence. 1,2 Squamous and basal cell carcinoma and Bowen's disease may occur in PK lesions, the former being most common. 5 Risk factors include extensive lesions located on the extremities and prolonged evolution period. 1,2,8 The oncogenic potential may be the result of an increased p53 expression in the keratinocytes near the cornoid lamella. 2,5 PK treatment can be done with topical medications, such as keratolytic, 5-fluorouracil 5%, retinoids, imiquimod, diclofenac, vitamin D derivatives, and cantharidin tacrolimus. 1 Cryotherapy, photodynamic therapy, dermabrasion, excision, CO 2 laser, and other lasers can be used with varying degrees of success. In disseminated or refractory lesions, oral retinoid may be beneficial despite the recurrence after discontinuation of the therapy. 1,5 Surgery is the most effective treatment. 1,8 In our case -considering that the patient had a local lesion and the possibility of cancer as reported by the literature -we opted to perform surgical removal of the entire lesion and to use a skin graft with excellent functional and aesthetic results for the patient. We point out that, although PK is not considered indicative of AIDS, its appearance or presence in HIV-infected patients could be an immunodeficiency marker.q