Disseminated superficial actinic porokeratosis
Published Web Locationhttps://doi.org/10.5070/D366j9q5jh
Disseminated superficial actinic porokeratosisThe Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, New York
Panta Rouhani MD PhD MPH, Max Fischer MD, Shane Meehan MD, Miriam Keltz Pomeranz MD
Dermatology Online Journal 18 (12): 24
Disseminated superficial actinic porokeratosis, which was described in 1966, is characterized by small, atrophic patches with distinctive keratin rims that occur on sun-exposed areas of the extremities, shoulders, and back. The diagnosis is based on the histopathologic finding of a cornoid lamella, absence of a granular layer, and often a thin epidermis. It is associated with exposure to ultraviolet radiation. Gene studies suggest a pathway defect in which several mutations in keratinocyte proliferation and differentiation lead to development of porokeratosis.
A 64-year-old woman presented to the New York University Dermatologic Associates eight years ago with a six-year history of a persistent eruption that involved her arms and legs. She reported an asymptomatic eruption on her arms and legs that first appeared during the summer months. The patient denied any pruritus or stinging sensation. She was treated with ammonium lactate 12 percent cream and 5-fluorouracil. Her current regimen includes ammonium lactate 12 percent cream and topical tretinion.
Past medical history included post-menopausal flushing, which was treated with hormone replacement therapy and aquagenic wrinkling of the palms. Family history and social history are non-contributory.
One year after her initial presentation, a shave biopsy from a representative lesion was obtained from the right upper arm. A second shave biopsy from a lesion on the left forearm was obtained two years later.
|Figure 1||Figure 2|
Scattered, erythematous, annular plaques with slightly elevated borders were present on the upper and lower extremities.
There is a sparse lymphocytic infiltrate in the upper part of the dermis, above which there is focal thinning of the epidermis and a cornoid lamella.
Porokeratosis was first described by Mibelli and Respighi in 1893 . It is now recognized that there are at least four clinical variants: porokeratosis of Mibelli, porokeratosis palmaris et plantaris disseminata, linear porokeratosis, and disseminated superficial actinic porokeratosis . The differential diagnosis of porokeratosis includes actinic keratoses, psoriasis, keratosis follicularis, nevoid basal-cell nevus syndrome, lichen nitidus, porokeratotic eccrine ostial and dermal duct nevus, hereditary punctuate keratoderma, and benign hamartoma of the eccrine sweat glands .
Disseminated superficial actinic porokeratosis (DSAP) is the most common form of porokeratosis . The term disseminated superficial porokeratosis was introduced in 1937 as a clinical variant of porokeratosis of Mibelli . A possible actinic etiology was described and the term DSAP was introduced in 1966 . It is characterized by multiple, small lesions on sun-exposed areas of the body. It has a slight female preponderance (1.76:1) and typically occurs on the extensor surfaces of the extremities, shoulders, and back as atrophic patches with a distinctive hyperkeratotic rim . It rarely occurs on the face . The distinctive rim of hyperkeratosis that is observed at the periphery of the lesion correlates with the histopathologic presence of the column of parakeratotic cells, which is known as the cornoid lamella . Below the column of parakeratotic cells, the granular-cell layer is absent and the epithelium often is thin .
DSAP usually appears during the third or fourth decade of life and is slowly progressive . At least one-half of patients experience exacerbations during the summer months as a consequence of sun exposure. Patients have also described exacerbations after exposure to ultraviolet B and A artificial light . One-third of patients experience pruritus or stinging sensations . Risk factors for DSAP include genetic factors, ultraviolet exposure, and immunosuppression. Patients with lighter skin pigmentation appear to be at higher risk. DSAP is inherited as an autosomal dominant condition, with reduced penetrance at younger ages . The development of a cornoid lamella suggest a focal, expanding clone of abnormal keratinocytes . Gene studies suggests a pathway defect in which several mutations in keratinocyte proliferation and differentiation lead to development of porokeratosis .
Treatment of DSAP includes keratolytic treatments, 5-fluorouracil 5 percent, topical imiquimod, diclofenac gel, and topical retinoids. The use of methyl aminolevulinate has also been reported to be successful in the treatment of DSAP [1, 10]. Other treatment options include cryotherapy, electrodesiccation, curettage, dermabrasion, and laser therapy . These destructive modalities are useful in patients with only one or a few porokeratotic lesions. Education regarding protection from sunlight and regular checks for malignant conditions is needed in patients with DSAP.
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