Published on 18/03/2015 by admin
Filed under Dermatology
Last modified 18/03/2015
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Agustin Martin-Clavijo and John Berth-Jones
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
The porokeratoses are a group of disorders of keratinization characterized by lesions with a peripheral keratotic ridge, manifesting histologically as a cornoid lamella. Terminology and classification are debated, but the main recognized forms are: (1) disseminated forms, of which disseminated superficial actinic porokeratosis (DSAP) is predominant; (2) porokeratosis of Mibelli (PM); (3) palmoplantar porokeratosis (porokeratosis palmaris, plantaris et disseminata – PPPD); (4) linear porokeratosis (LP). An autosomal dominant mode of inheritance has been reported in the disseminated form. Overexpression of the p53 tumor suppression protein has been identified in the cornoid lamella. Porokeratotic lesions are progressive and carry malignant potential, especially large long-standing lesions and the linear variants. In addition, the lesions can cause pruritus and represent a cosmetic problem for some patients.
The family history should be reviewed and the patient’s immune function assessed, particularly with the disseminated forms. Discontinuation of immunosuppression has led to resolution of lesions in some patients.
Treatment of porokeratoses may be indicated, not only for cosmetic benefit and symptomatic relief, but also to reduce the risk of malignancy. Optimal therapy is dependent on the type and extent of porokeratosis, and the level of concern over malignant progression. Management should include avoidance of irradiation (UV or X-rays) and observation for signs of malignant transformation (squamous cell carcinoma, basal cell carcinoma, Bowen’s disease).
The lesions are usually asymptomatic. When present, pruritus associated with disseminated lesions is often responsive to topical corticosteroids. The palmoplantar variant may cause functional disability due to pain and discomfort.
Localized disease responds to ‘surgical’ methods such as cryotherapy, CO2 laser, curettage and cautery, or excision, but these can result in significant scarring, especially when the lesions are numerous.
Topical 5-fluorouracil, imiquimod, and vitamin D analogs can be helpful, but only partial responses are likely in DSAP. Inflammatory reactions are likely when using 5-fluorouracil or imiquimod and indicate a greater likelihood of response. With some caution, these modalities can be used under occlusion, treating one area at a time. In the authors’ experience results are inconsistent, even with occlusion.
Systemic retinoids have been effective in localized and systemic disease, but there have been reports of exacerbation of pre-existing lesions. Recurrence is common on discontinuation of therapy, and a long-term maintenance dose may be required. This modality might also reduce the risk of malignant transformation.
There is one report of genital DSAP responding partially to topical diclofenac, but a subsequent case series demonstrated very limited benefit. There are also reports of the effectiveness of topical retinoids, dermabrasion, pulsed dye laser, Nd : YAG laser, corticosteroids, and topical photodynamic therapy. Treatments used in combination have included CO2 laser and tacalcitol, CO2 laser and photodynamic therapy, and 5-fluorouracil and imiquimod.
Skin biopsy
Dermoscopy
Assessment of immune function
Delfino M, Argenziano G, Nino M. J Eur Acad Dermatol Venereol 2004; 18: 194–5.
Dermoscopic examination of DSAP showed a characteristic central scar-like area with a single or double ‘white track’ structure at the margin. The histopathologic correlate of the linear structure was shown to be the cornoid lamella.
Dereli T, Ozyurt S, Osturk G. J Dermatol 2004; 31: 223–7.
Eight patients with 20 lesions received treatment with 30-second cycles of cryospray followed by sharp dissection of the lesion border. Most lesions resolved after one treatment; two required one further treatment.
Limmer BL. Arch Dermatol 1979; 115: 582–3.
Twenty-one lesions of porokeratosis in 11 patients were treated with cryotherapy, resulting in a cure rate of 90.5%. The lesions were pared prior to treatment. There was no evidence of recurrence over an average follow-up period of 22 months.
Gonçalves JC. Arch Dermatol 1973; 108: 131–2.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
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Cryotherapy
5-Fluorouracil
Imiquimod
Vitamin D3 analogs
