A 45-year-old woman is concerned about a lesion on her left calf that has gradually been increasing in size over the past several months. The patient is moderately obese and takes oral medication to control diabetes and hypertension. Physical examination reveals a well-demarcated, 2-cm, asymptomatic, erythematous plaque with central atrophy and a slightly elevated border. No similar lesions are noted elsewhere on the patient’s body.
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Classic porokeratosis (porokeratosis of Mibelli) was originally named for the Italian clinician Vittorio Mibelli, who first wrote about the condition in 1893.1 The lesion begins as a hyperpigmented scaly papule that expands outwardly, resulting in an erythematous plaque with an atrophic center and a hyperkeratotic, slightly raised border.2 The majority of lesions are asymptomatic, and complaints of pruritus or bleeding are uncommon.
Porokeratosis is most commonly located on the trunk and extremities and is most prevalent in middle-aged individuals. Histopathology is distinctive and characterized by the presence of a cornoid lamella that is composed of a thin column of parakeratotic corneocytes embedded within the stratum corneum (outermost layer of the epidermis).2,3
Other conditions characterized by porokeratosis include disseminated superficial actinic porokeratosis, linear porokeratosis, and porokeratosis palmaris et plantaris disseminata. Porokeratosis is believed to result from clonal expansion of atypical epidermal keratinocytes.4
Various treatment options may prove effective in treating porokeratosis, including surgery, cryosurgery, laser ablation, 5-fluorouracil cream, topical retinoids, potent topical corticosteroids, and topical tacrolimus.4,5 If a patient elects not to treat, use of sunscreen and periodic observation are prudent. Although rare, porokeratosis may develop into a malignancy.6
Stephen Schleicher, MD, is director of the DermDox Center for Dermatology, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
1. Allegra F. The man behind the eponym. Vittorio Mibelli and the tale of “porokeratosis.” Am J Dermatopathol. 1986;8(2):169-172.
2. Sertznig P, von Felbert V, Megahed M. Porokeratosis: present concepts. J Eur Acad Dermatology Venereol. 2012;26(4):404-412.
3. Ferreira FR, Santos LD, Tagliarini FA, Lira ML. Porokeratosis of Mibelli. Literature review and a case report. An Bras Dermatol. 2017;88(6 Suppl 1):179-182.
4. Kanitakis J. Porokeratoses: an update of clinical, aetiopathogenic and therapeutic features. Eur J Dermatol. 2014;24(5):533-544.
5. Weidner T, Illing T, Miguel D, Elsner P. Treatment of porokeratosis: a systematic review. Am J Clin Dermatol. 2017;18(4):435-449.
6. Zhang F, Bai W, Sun S, Li N, Zhang X. Squamous cell carcinoma arising from giant porokeratosis and rare postoperative recurrence and metastasis: a case report. Medicine (Baltimore). 2020;99(2):e18697.