Porokeratosis is an epidermal disorder characterized by annular lesions surrounded by raised, keratotic borders with a characteristic histopathologic feature, the so-called cornoid lamellae. At least 5 types of porokeratosis have been identified. Reports have described porokeratosis occurring rarely on the genitalia, oral mucosa, cornea, and face, but the extremities are most frequently involved.1–3
Porokeratosis, first characterized in 1893, can be classified according to its clinical appearance. The classic plaque type, Mibelli porokeratosis, and disseminated superficial actinic porokeratosis are the 2 types most commonly observed. Others include porokeratosis palmaris plantaris et disseminata, porokeratosis punctata palmaris et plantaris, and linear porokeratosis. Single or multiple plaques with elevated borders and variably atrophic centers characterize the lesions.
A rare syndrome associated with porokeratosis is known as familial craniosynostosis, anal anomalies, and porokeratosis (CAP syndrome). One report has described the syndrome in 2 brothers.4 A third male sibling and the parents were phenotypically normal, suggesting an autosomal recessive inheritance, although X-linked inheritance or gonadal mosaicism could not be excluded.
Exclusive facial porokeratosis is rare (Table I), although 15% of patients with disseminated superficial actinic porokeratosis have facial lesions. A published report has described 15 cases of solar facial porokeratosis presenting as scaly papules on the nose and adjacent perinasal areas induced and exacerbated by sunlight exposure.5 Of the 15 cases, 12 were women, leading the researchers to characterize the disease as one of young women.
|Citation||No. of Cases||Comments|
|Sharquie and Al-Baqhdady, 20035||15||12 women, 3 men|
|Rahbari et al, 19951||2||Destructive|
|Nabai and Mehregan, 19792||2||Nondestructive|
|Mehregan et al, 19803||7||Nondestructive|
Treatments for porokeratosis advocated with variable success rates include keratolytics, cryotherapy, carbon dioxide laser, oral retinoids, and excision. Two patients have been described with unusual extensive destructive porokeratosis lesions on the face, which partially responded to oral etretinate, topical 5-flourouracil, and topical steroids.1 Seven other patients with nondestructive facial lesions responded poorly to therapy.3 Our patient has had a trial of cryotherapy with moderate improvement of facial lesions.
Some researchers6 have suggested that porokeratosis forms as a result of a mutant clone of epidermal cells occurring and expanding peripherally from the base of the parakeratotic column. Inhibitory forces exerted by a classical immune mechanism may contain this mutant clone and prevent macroscopic lesions from developing. Immunosuppressive therapy can give rise to porokeratosis, although in our case there was no evidence of immunodeficiency. Cases have been reported of facial porokeratosis developing after a candidal skin infection.7
Squamous cell carcinoma, Bowens disease, and basal cell carcinomas have been reported to originate from solitary and multiple lesions of porokeratosis.8 Malignant transformation has been described in all types of pororkeratosis but is most common in linear porokeratosis and rare in disseminated superficial actinic porokeratosis. Immunosuppressed patients are at higher risk of developing aggressive squamous cell carcinomas from lesions of porokeratosis, as in the case of metastatic squamous cell carcinoma in a renal transplant patient9 and a case of fatal metastatic squamous cell carcinoma arising from porokeratosis in an immunosuppressed patient.10 No evidence of malignancy was found in our patient's biopsy. To date, malignant degeneration has not been reported in any of the published cases of solar facial porokeratosis. Thus far, our patient does not show any clinical evidence of malignancy.