Disseminated superficial actinic porokeratosis (DSAP) is a chronic condition characterized by numerous atrophic papules and patches with a distinctive peripheral keratotic ridge, typically found on sun-exposed areas.1,2 Treatment of DSAP is warranted not only for cosmetic and symptomatic benefits but also to prevent malignant transformation.3,4 Successful treatment of DSAP often is difficult and frequently requires the use of multiple modalities. Ingenol mebutate gel 0.05% is a topical medication primarily used for the treatment of actinic keratosis (AK) by inducing cell death.5 We report a case of DSAP treated effectively with ingenol mebutate gel 0.05%.
Case Report
A 37-year-old woman was referred to the dermatology department for counseling for pseudoxanthoma elasticum (PXE), which had been proven on biopsy by an outside dermatologist 2 years prior. Physical examination revealed yellow papules on the neck that were characteristic of PXE, but no lesions were noted on the arms or legs. The only other cutaneous finding was a soft nodule on the right hip consistent with a lipoma. The patient returned to our institution 6 years later with lesions on both lower legs. She reported that these lesions had been present for 3 years and were exacerbated by sun exposure. On physical examination, multiple scattered, erythematous, annular, scaling papules and plaques were noted on the bilateral legs. A biopsy showed the histopathologic findings of DSAP (Figure 1). The patient had no family history of DSAP or PXE.
Figure 1. Stratum corneum with alternating orthokeratosis and parakeratosis overlying an epidermis with focal dysplasia. The epidermis showed a short vertical column of parakeratosis overlying an area of dyskeratosis consistent with disseminated superficial actinic porokeratosis (H&E, original magnification ×20).
To determine the best treatment modality, we treated 4 test areas on both upper and lower legs: one with trichloroacetic acid (TCA), one with cryotherapy, one with imiquimod cream 5%, and one with tretinoin cream 0.1%. The patient returned 4 weeks later and showed modest response to TCA, cryotherapy, and tretinoin cream. Because cryotherapy was determined to be most effective, 20 more lesions were frozen at that visit. Over the next 2 years, the patient was treated with TCA, imiquimod cream 5%, and tretinoin cream 0.1%, but all ultimately proved ineffective for DSAP.
The patient returned 2 years after treatment failure (age 47 years) and was prescribed ingenol mebutate gel 0.05% for 2 days over an area of 25 cm2 on the right lower leg (Figure 2A). She returned for follow-up at days 3, 15, 30, and 60. At day 3, the patient developed an inflammatory response to the medication with moderate erythema and scaling of individual lesions. No vesiculation, pustulation, edema, or ulceration was exhibited (Figure 2B). At day 30, there was a marked reduction in scaling with some postinflammatory erythema (Figure 2C). At day 60, much of the erythema had faded and the scale remained notably reduced (Figure 2D).
Figure 2. Disseminated superficial actinic porokeratosis with multiple erythematous, annular, scaling papules on the patient’s right lower leg at baseline (A). At day 3 following treatment with ingenol mebutate gel 0.05%, the patient developed an inflammatory response to the medication with moderate erythema and scaling of individual lesions (B). At day 30, a marked reduction in scaling with some postinflammatory erythema was noted (C). At day 60, much of the erythema had faded and the scale remained notably reduced (D).