Letter to the Editor
To the Editors:
Porokeratosis is a rare genetically determined disorder of epidermal keratinization. Sporadic cases can also occur through somatic mutations.1
Labial porokeratosis is believed to represent an uncommon subtype of porokeratosis of Mibelli (PM). We report the case of a woman with a solitary plaque of porokeratosis on the lips.
A 50-year-old woman presented with a 3-year history of slowly progressive, asymptomatic, oval, whitish plaque with an atrophic center and slightly hyperkeratotic edge on her lower and upper lips (Fig. 1). She had no other lesions on her skin or mucous membranes. There was no family history of a similar condition. A 4-mm punch biopsy specimen of the peripheral ridge was obtained. Histopathologic examination showed a dense parakeratotic column, known as the cornoid lamella, with underlying hypogranulosis and vacuolated keratinocytes, changes characteristic of porokeratosis (Figs. 2, 3). No lymphoid infiltrate was present in the dermis. A histologic diagnosis was made, and the lesion was considered to be a single plaque of PM. The patient is still being treated with cryotherapy and CO2 laser vaporization, with good response.
The classical form of PM, described in 1893 by Mibelli, consists of a single or multiple annular and gyrate plaques with an atrophic center bordered by a peripheral grooved keratotic ridge.2 It usually has onset in childhood but may appear at any age, especially in nonhereditary cases. Lesions show a tendency to centrifugal spread and appear most often on the limbs and genitalia, although any part of the body may be affected, including palms and soles. A solitary lesion of porokeratosis is exceptionally seen on the lips.2,3 To our knowledge, only approximately 5 cases have been reported to date in the literature in the past 45 years.2-5
This report shows some differential histologic features such as the absence of characteristic hyperkeratosis and dermal lymphocytic infiltrate beneath the cornoid lamella. In conclusion, the unusual location and some atypical features may justify considering this entity as a distinct type of porokeratosis. Further studies will be required because of the small number of reports.
Pablo Hernández Bel, MD
Department of Dermatology, Valencia General University Hospital and Medical School Valencia, Spain
Onofre Sanmartín Jimenez, MD
Guillermo Sorni Bröker, MD
Carlos Guillén Barona, MD, PhD
Department of Dermatology, Fundación Instituto Valenciano de Oncología Valencia, Spain
1. Malek J, Chedraoui A, Kibbi AG, et al. Genitogluteal porokeratosis: 10 years to make the diagnosis! Am J Dermatopathol
2. Vergara G, Bañuls J, Botella R, et al. Porokeratosis of the lower lip. Eur J Dermatol
3. Rosón E, García-Doval I, De La Torre C, et al. Disseminated superficial porokeratosis with mucosal involvement. Acta Derm Venereol
4. Dupre A, Christol B. Mibelli's porokeratosis of the lips. Arch Dermatol
5. Schnitzler L, Verret JL, Baudoux C. Porok'eratose de Mibelli de la lèvre. Ann Dermatol Venereol