The patient is a 58-year-old Caucasian male with no significant past medical history who presented to our clinic with annular plaques since the age of one. The two most significant lesions are located on his right hand and right foot. They have increased slowly in size in proportion with the patient’s growth. They have been asymptomatic, and previously diagnosed as “atypical warts.”
On the right third digit, there is a well-demarcated, annular plaque with a hyperkeratotic, verrucous border and atrophic center. A similar annular lesion is also present on the right foot.
Shave biopsy of the third digit shows an epidermis with acanthosis, hypergranulosis, and compact hyperkeratosis. A groove was present in the center of the biopsy. This groove contained a column of parakeratosis with loss of the granular layer and dyskeratotic keratinocytes consistent with a cornoid lamella.
Keratolytics, such as Carmol-40 or Lac-Hydrin, were discussed, but the patient does not desire any treatment at this time. Regular follow-ups are planned to monitor for signs of malignancy.POROKERATOSIS OF MIBELLI
Porokeratosis is a disorder of abnormal keratinization first described by Vittorio Mibelli in 1893.1 Several clinical forms of porokeratosis have been described including: Porokeratosis of Mibelli, linear porokeratosis, porokeratosis punctata palmaris et plantaris, disseminated superficial porokeratosis, and disseminated superficial actinic porokeratosis. These clinical variations may represent phenotypic variations of the same genetic defect. Genes frequently affected include the p53 tumor suppression gene or those involved in wound healing, epidermal differentiation, and intercellular communication.2, 3 Additionally, environmental modifications, such as irradiation, trauma, or immunosuppression, may play a role.4
The “cornoid lamella” is the hallmark of porokeratosis. This characteristic clinical and histologic finding of columns of parakeratotic cells represents hyperproliferation of atypical keratinocytes that form a raised boundary between normal and abnormal cells.5 Compared to other clinical variants, Porokeratosis of Mibelli exhibits wider, deeper invaginations into the epidermis with prominent adjacent papillomatosis.5 Disease onset is usually in childhood although it may present at any age.5, 6 Lesions typically grow slowly, although rapid growth can be observed in the context of immunosuppression.5
Treatment of porokeratosis may be challenging and is sometimes recommended due to the potential for malignant transformation. In a review of 281 reported cases of porokeratosis, 21 (7.5%) revealed a malignancy arising within the lesion.7 The greatest risk factors for malignant transformation were large size, long standing duration, and the presence of linear porokeratosis.7 Successful treatments reported include: topical fluorouracil and subsequent photodynamic therapy,5 topical retinoids,4 oral retinoids,8 imiquimod (5x/week for 6 weeks),9 cryosurgery,10 pulsed dye laser, C02 laser vaporization,11 and dermabrasion.12
1. Mibelli V. Contributo allo studio della ipercheratosi dei canali sudoriferi. G Ital Mal Ven Pell. 1893;28:313.
2. Zhang ZH, Wang ZM, Crosby ME, et al. Gene expression profiling of porokeratosis. J Cutan Pathol. Nov 2008;35(11):1058-1062.
3. Magee JW, McCalmont TH, LeBoit PE. Overexpression of p53 tumor suppressor protein in porokeratosis. Arch Dermatol. Feb 1994;130(2):187-190.
4. Palleschi GM, Torchia D. Porokeratosis of Mibelli and superficial disseminated porokeratosis. J Cutan Pathol. Feb 2008;35(2):253-255.
5. Levitt J, Emer JJ, Emanuel PO. Treatment of porokeratosis of mibelli with combined use of photodynamic therapy and Fluorouracil cream. Arch Dermatol. Apr;146(4):371-373.
6. Pizzichetta MA, Canzonieri V, Massone C, Soyer HP. Clinical and dermoscopic features of porokeratosis of Mibelli. Arch Dermatol. Jan 2009;145(1):91-92.
7. Sasson M, Krain AD. Porokeratosis and cutaneous malignancy. A review. Dermatol Surg. Apr 1996;22(4):339-342.
8. Uenishi T, Teramura K, Kitamura M, et al. Hyperkeratotic variant of porokeratosis Mibelli with dermal amyloid deposits. J Dermatol. May;37(5):475-479.
9. Montes-De-Oca-Sanchez G, Tirado-Sanchez A, Garcia-Ramirez V. Porokeratosis of Mibelli of the axillae: treatment with topical imiquimod. J Dermatolog Treat. 2006;17(5):319-320.
10. Dereli T, Ozyurt S, Ozturk G. Porokeratosis of Mibelli: successful treatment with cryosurgery. J Dermatol. Mar 2004;31(3):223-227.
11. Rabbin PE, Baldwin HE. Treatment of porokeratosis of Mibelli with CO2 laser vaporization versus surgical excision with split-thickness skin graft. A comparison. J Dermatol Surg Oncol. Mar 1993;19(3):199-202.
12. Spencer JM, Katz BE. Successful treatment of porokeratosis of Mibelli with diamond fraise dermabrasion. Arch Dermatol. Sep 1992;128(9):1187-1188.
well-demarcated, annular plaque with a hyperkeratotic, verrucous border and atrophic center