Response to photodynamic therapy for pustular dermatosis of the scalp and hypertrophic actinic keratosis.

Erosive pustular dermatosis of the scalp is a rare inflammatory skin disease that mainly affects older patients and is characterized by the presence of sterile pustules and scabs. Recently, several authors have reported the usefulness of photodynamic therapy in the treatment of this condition. We present the case of a 79-year-old man with skin phototype III and actinic keratosis of the face and scalp, occasionally treated with cryotherapy, after which the patient would complain of painful erosions in the treated area. On one of his check-up visits he had an outbreak of pustules and scabs that mainly affected the posterior part of the parietal region. The pustules had an erythematous base, and painful erosions and scabs were also visible. Biopsy revealed areas of fibrosis, a predominantly perifollicular neutrophil infiltrate, and areas of scarring. The diagnosis was erosive pustular dermatosis of the scalp, which responded favorably to topical treatment with fusidic acid plus betamethasone cream and healed with scarring alopecia. Thereafter, actinic keratoses in this patient were successfully treated with topical imiquimod to prevent outbreaks of pustulosis. During follow-up, however, he presented with hypertrophic actinic keratoses in the occipital region and numerous pustules that coalesced into lakes of pus (Fig. 1). These actinic keratoses did not respond to imiquimod and the erosive pustular dermatosis of the scalp worsened with the use of this agent. It was then decided to try treatment with photodynamic therapy (PDT). At the first session, curettage of the most hypertrophic actinic keratoses was performed and this was followed by an application of Metvix (160 mg/g methyl aminolevulinate hydrochloride cream; manufac-