What is Disseminated Superficial Actinic Porokeratosis (DSAP)?
Disseminated superficial actinic porokeratosis (DSAP) is a chronic disorder of keratinization characterized by multiple small brown papules and plaques with distinctive elevated keratotic rims, occurring predominantly on sun-exposed areas of the extremities, typically manifesting in the third or fourth decades of life with a strong female predominance. 1, 2
Clinical Characteristics
DSAP presents as numerous atrophic patches rimmed by a ridge of keratin on sun-exposed sites, most commonly the distal extremities (arms and legs), appearing as small brown plaques with raised borders 1, 3
The condition typically begins in the third or fourth decade of life and shows a female preponderance, distinguishing it from other forms of porokeratosis 1
Lesions are usually asymptomatic but cosmetically concerning, and the condition is chronic and progressive over time 2, 4
Pathological Features
The diagnostic hallmark is the cornoid lamella at the lesion margin, which represents a column of parakeratotic cells extending through the stratum corneum and is thought to represent a clonal keratinocyte proliferation 1, 3
Histologically, DSAP shows infrequent cornoid lamellae separated by atrophic epidermis, in contrast to other variants like verrucous porokeratosis which demonstrate epidermal hyperplasia with multiple, almost contiguous, broad cornoid lamellae 3
Clinical Significance and Malignant Potential
DSAP poses a risk for malignant transformation to squamous cell carcinoma, making it more than just a cosmetic concern and emphasizing the need for monitoring and management 2
DSAP is the most common of five clinical variants of porokeratosis (the others being Mibelli, linear, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis), and can occasionally coexist with other forms 1, 3
Diagnostic Considerations
DSAP is often misdiagnosed as chronic UV-damage or actinic keratoses, leading to years of inappropriate treatment with limited success 5
The key distinguishing feature from actinic keratoses is the characteristic raised keratotic rim (cornoid lamella) surrounding atrophic centers, whereas actinic keratoses present as discrete patches of erythema and scaling without this distinctive border 6, 1
Treatment Landscape
Current treatment options include topical diclofenac gel, imiquimod, ingenol mebutate, cryosurgery, photodynamic therapy, chemical peels, and topical or systemic retinoids, though evidence remains largely anecdotal with limited high-quality clinical trial data 1, 5, 2
Many patients remain refractory to multiple therapeutic options, with case series showing patients treated unsuccessfully for an average of 14.4 years before finding effective management 5
There is currently a paucity of high-quality clinical trial data to guide treatment decisions, with most evidence coming from case reports and small case series rather than randomized controlled trials 2, 4