Dermatology Online Journal

Isolated single digit Porokeratosis of Mibelli: An unusual case
Samuel Odeyinde MBBS FWACS (Plast) MRCS (Eng), Harry Belcher MS FRCS (Plast)
Dermatology Online Journal 18 (10): 13

Queen Victoria Hospital, East Grinstead, West Sussex, United Kingdom

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Abstract

Porokeratosis of Mibelli is an uncommon dermatosis, which may be associated with immunosuppression and which may undergo malignant transformation. We report a patient with a chronic history of a skin lesion of his right 5th finger that was histologically confirmed to be Porokeratosis of Mibelli. Although it commonly affects the extremities, the isolated involvement of an individual digit of the hand has not been previously reported.

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Introduction

Porokeratosis of Mibelli is an uncommon dermatosis, which may be associated with immunosuppression and may undergo malignant transformation. Although it commonly affects the extremities, a search of published literature did not reveal any reported cases isolated to an individual digit of the hand. Our unit recently managed a patient with a chronic history of a skin lesion of his right 5th finger that was histologically confirmed to be Porokeratosis of Mibelli.

Case report

A 47-year-old man was referred to our unit by his dermatologist. He had a 3-year history of frequent breakdown of the skin over the dorsal aspect of the proximal interphalangeal (PIP) joint of his right 5th finger. There was no obvious precipitating cause and no involvement of any other part of his body. He was otherwise in good health and had no family history of a similar skin disorder. A biopsy of the area done a year previously was inconclusive, showing a hypertrophic dermis with inflammation of the upper part and no ulceration.

Examination revealed a 15 mm by 5 mm ulcer overlying the dorsal aspect of the proximal interphalangeal joint of his right 5th finger with surrounding erythema (Figure 1). There were no functional deficits observed.

Figure 1	Figure 2

He was treated with excision of the plaque and application of a full thickness skin graft with an uneventful recovery. Histopathology showed parakeratosis, hypergranulosis, and irregular acanthosis with spongiosis and a perivascular lymphohistiocytic infiltrate in the underlying dermis. The spongiotic epidermis with overlying parakeratosis was delimitated by a peripheral cornoid lamella (Figure 2). The features were diagnostic of Porokeratosis of Mibelli, which had been completely excised. His subsequent care was handed back to his dermatologist.

Discussion

Porokeratosis is a clonal disorder of keratinization characterized by one or more atrophic patches surrounded by a clinically and histologically distinctive ridge-like border called the cornoid lamella [1, 2].

Risk factors for the development of porokeratosis include genetic inheritance, ultraviolet radiation, and immunosuppression [3]. Malignant degeneration (squamous and basal cell carcinomata) has been reported in all forms of porokeratosis. Porokeratosis of Mibelli often appears in childhood, but lesions may be present at birth or may first appear at puberty or later. Adult onset has been seen following suppression of the immune system by certain medications or illness [4].

Porokeratosis of Mibelli most often affects the limbs, particularly the hands and feet, the neck and shoulders, the face and the genitals. However, any part of the body may be affected including the mucous membranes [2, 4]. The involvement of an individual digit of the hand, in isolation, is not a common occurrence in the literature.

There are a variety of treatment options for porokeratosis such as cryotherapy, topical 5FU, topical retinoids, lasers, shave excision, and dermabrasion. All of these modalities are variable in outcome [2]. Complete surgical excision, as in this case, should offer a cure. Although, in widespread cases, non-operative treatment may be more appropriate.

The prognosis is generally excellent. The unusual feature in this case was isolated involvement of a single digit.

ACKNOWLEDGEMENTS: We would like to thank Dr M. Fallowfield, Consultant Histopathologist at the Queen Victoria Hospital, East Grinstead, for the photomicrograph and histology report.

References

1. Spencer LV. Porokeratosis. eMedicine from WebMD [Internet]. Updated May 7, 2010. Available at: http://emedicine.medscape.com/article/1059123-overview. Accessed January 15, 2012.

2. Cockerell CJ, Larsen F. Benign epidermal tumors and proliferations. In: Bolognia JL, Jorizzo JL, Rapini RP, Horn TD, Mascaro JM, Mancini AJ, et al (eds). Dermatology, Edinberg: Mosby; 2008: 1668-1671.

3. Zenarola P, et al. Exacerbation of porokeratosis: a sign of immunodepression. J Am Acad Dermatol 1993;29:1035-1036. [PubMed].

4. Porokeratosis of Mibelli. DermNetNZ [Internet]. New Zealand: New Zealand Dermatological Society, Incorporated; 2003 [updated July 1, 2011]. Available at: http://www.dermnetnz.org/scaly/porokeratosis-mibelli.html. Accessed January 15, 2012.

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