Vanishing seborrhoeic keratosis.

Seborrhoeic keratosis (SK) is the most common benign tumor of middle and older ages (1), and can appear in any part of the body except mucous membranes. Its clinical diagnosis is almost always easy and usually offers no problems. Unlike common SK, the inflammatory variety of the disease is often difficult to diagnose and may be clinically confused with basal cell carcinoma, squamous cell carcinoma, and even malignant melanoma (2,3), with eczematous changes in and around SK with an unknown cause. On the other hand, only 8% of cases of inflammatory SK occur on the extremities (2).We report on a patient with an eczematous SK located on one leg, with complete regression a few months after inflammation. An 89-year-old man with no history of relevant diseases was admitted for a red, slightly elevated, desquamative inflammatory plaque covered with haemorrhagic crusts located on the frontal and inner aspect of his right leg. The lesion measured about 3 centimeters in diameter and had appeared 6 months earlier (Figure 1). Dermoscopy was not performed. A biopsy of the lesion was done, with the presump-tive clinical diagnosis of basal cell carcinoma, squa-mous cell carcinoma, or amelanotic melanoma. The skin biopsy specimen showed an epidermis with acanthosis, hyperplasia of basaloid keratinocytes, and horn pseudocysts with parakeratotic and ortho-hy-perkeratosis, along with lymphoid exocytosis, spon-giosis, and necrosis of keratinocytes. There was an inflammatory infiltrate in the der-mis, without athypic characteristics (Figures 2 and 3). During suture removal in the second week, the presence of pus was detected, so the patient was treated with oral flucloxacillin at 500 mg every 8 hours for 7 days, as well as topical chloramphenicol. After initial improvement, the lesion worsened and eczema appeared at day 40; a cream containing 0.05% be-tamethasone dipropionate 0.1% and gentamicin sulfate was then administered 2 times per day. One month later, the lesion had completely disappeared, showing only a slight postinflammatory hyperpig-mentation (Figure 4). The first spontaneous regressions of SK were reported in two patients with multiple lesions. The first case occurred after an exfoliative erythroderma with the inflammation of preexisting SK and also the appearance of new ones, which was associated with a benign renal cyst (4): The second patient, who presented with pruritus of the trunk and extremities that had lasted for 1 month, showed multiple inflammato-ry SK along with a concomitant nasal adenocarcino-ma with an evolution of two years, which produced nasal obstruction (5). …