LAUSR

Ingenol mebutate gel is an effective treatment for actinic keratoses on the head and body, with local reactions of generally low-tointermediate intensity and short duration usually subside within 15 days (Lebwohl et al., 2012). We present two cases, a 74-years-old man with a history of actinic keratosis previously treated with cryotherapy and an 85-years-old man with a history of actinic keratosis previously treated with ALA 10% photodynamic therapy. In both cases, the recurrence of lesions was treated with topical application of ingenol mebutate gel 0.015% (Picato) once daily, for three consecutive days, over a 25 cm area. The patients came back to our attention 35 days and 25 days, respectively, after the last application of ingenol mebutate. At clinical examination, skin surface appeared healthy except for the scalp, which, in the treated area, showed erythema with pustules and crusts. After gentle removal of some crusts, we observed leakage of serum-purulent material in the context of atrophic skin, with large telangiectasias. Bacteriologic and mycologic investigations were negative. Underlying systemic diseases were excluded on the basis of clinical examination and laboratory data, including routine exams and autoimmunity pattern. Both patients were treated with oral methylprednisolone (16 mg daily, with progressive reduction) and a 0.05% clobetasol propionate foam. After eight weeks of treatment, complete resolution of the lesions was observed, except some scarring alopecia areas. The clinical features, laboratory data and history of treatment with ingenol mebutate were consistent with a diagnosis of erosive pustular dermatosis of the scalp (EPDS). Biopsy was refused by both patients, but it was not considered decisive, because the clinical setting and its rapid resolution with treatment also supported the clinical diagnosis. The only differences between the two clinical cases were the extent of the disease and the time of onset. In the first case, erythema with pustules and crusting was confined to the area treated with ingenol mebutate, (Figure 1) while in the second case it was disseminated beyond the treated area, but restricted approximately to the site of previous treatment with ALA (Figure 2). EPDS is an inflammatory chronic disease affecting usually elderly people, with extensive pustular lesions, erosions, and crusting of the scalp (Vaccaro, Guarneri, Barbuzza, & Guarneri, 2008). This condition usually leads to scarring alopecia of the affected areas. The trigger factor setting off this condition is very often a local trauma (i.e., surgery cryotherapy, radiotherapy, imiquimod, topical florouracil, tretinoin, photodynamic therapy, latanoprost) in the context of sun damaged scalp skin (Borgia, Guarneri, Guarneri, & Vaccaro, 2005; Guarneri, & Vaccaro, 2009; Rongioletti, Delmonte, Rossi, Strani, & Rebora, 1999; Starace et al., 2017; Toda et al., 2012; Vaccaro, Barbuzza, & Guarneri, 2009). The median time between the triggering event and the onset of the first signs of EPDS was generally 6 months (Starace et al., 2017).