Disseminated Superficial Actinic Porokeratosis

Disseminated superficial actinic porokeratosis (DSAP) is a disease of disordered keratinization. This condition represents 1 of 6 porokeratosis variants and involves more extensive distribution than most others. Linear porokeratosis, porokeratosis of Mibelli, punctate porokeratosis, porokeratosis palmaris et plantaris disseminata, and disseminated superficial porokeratosis comprise the remaining 5 variants. Other rare forms include porokeratosis ptychotropica, facial porokeratosis, giant porokeratosis, hypertrophic verrucous porokeratosis, reticulate porokeratosis, and eruptive pruritic papular porokeratosis. The eruptive form has been linked to malignancy, immunosuppression, and a pro-inflammatory state. Lesions develop across the body. Risk factors for porokeratosis include genetic predisposition, immunosuppression, and ultraviolet light exposure. A defining feature of all porokeratosis variants is the cornoid lamella, which appears histologically as a column of parakeratotic cells. This structure is characterized by a raised ridge circumscribing porokeratotic lesions. DSAP lesions begin as pink to brown papules and macules with a raised border in sun-exposed areas. These lesions may be asymptomatic or mildly pruritic. DSAP is considered precancerous, with a 7.5% to 10% risk of malignant transformation to squamous cell carcinoma (SCC) or basal cell carcinoma (BCC). Multiple treatment options exist, including topical diclofenac, photodynamic therapy (PDT), 5-fluorouracil (5-FU), imiquimod, vitamin D analogs (eg, calcipotriene), retinoids, and lasers.