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A 79-year-old man presents with a recurring, asymptomatic lesion of his right foot. Diagnosed elsewhere as a fungus, the condition failed to respond to topical antifungal therapies. Medical history included hypertension for which he took an oral diuretic medication. Examination of the right lateral ankle revealed a 2.5cm x 3.0cm sharply marginated, erythematous, annular patch. A hyperkeratotic ridge marked the leading edge of the lesion, and the center of the lesion appeared slightly hyperpigmented and atrophic. With the exception of significant photodamage to his face and neck, no other cutaneous abnormalities were observed.
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The patient was diagnosed with porokeratosis of Mibelli, the most common form of porokeratosis. Porokeratosis is a disorder of keratinization that affects males more than females and may arise in childhood, puberty, or in later years. These lesions characteristically present on an extremity as a sharply demarcated, annular patch with an atrophic center. The majority are asymptomatic.1
Histologically, porokeratosis is characterized by a cornoid lamella, which consists of tightly packed parakeratotic cells arranged in columns.1 These parakeratotic cells are usually benign in nature but have the potential for malignant transformation, most commonly squamous cell carcinoma. The incidence of transformation to a skin cancer is 7.5% to 11%.2,3
Many treatment options for porokeratosis of Mibelli have been described, including cryotherapy, 5-fluorouracil, imiquimod, topical retinoids, electrodessication and curettage, dermabrasion, and laser ablation.1,4,5 If lesions are asymptomatic and cosmetically acceptable, patients can be observed periodically for changes and monitored for skin cancer. Sun protection is advised to help prevent malignant transformation.
Megha D. Patel is a student at the Commonwealth Medical College, Scranton, Pennsylvania.
Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College and an adjunct assistant professor of dermatology at the University of Pennsylvania Medical College. He practices dermatology in Hazleton, Pennsylvania.
References
- Sertznig P, von Felbert V, Megahed M. Porokeratosis: Present concepts. J Eur Acad Dermatol Venereol. 2012;26(4):404-412.
- Goerttler EA, Jung EG. Porokeratosis Mibelli and skin carcinoma: A critical review. Humangenetik. 1975;26(4):291-296.
- Otsuka F, Someya T, Ishibashi Y. Porokeratosis and malignant skin tumors. J Cancer Res Clin Oncol. 1991;117(1):55-60.
- Agarwal S, Berth-Jones J. Porokeratosis of Mibelli: Sucessful treatment with 5% imiquimod cream. Br J Dermatol. 2002;146(2):338-339.
- McDonald SG, Peterka ES. Porokeratosis (Mibelli): Treatment with topical 5-fluorouracil. J Am Acad Dermatol. 1983;8(1):107-110.
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