Paederus fuscipes dermatitis : a report of nine cases observed in Italy and review of the literature

Paederus sp. is a beetle belonging to Staphylinidae family and Coleoptera order. Its distribution is worldwide, especially in hot climates. Over 600 species of Paederus are known, approximately 50 are able to cause an irritant contact dermatitis. When the beetle is accidentally crushed on the skin, it releases pederin, a potent toxin with vesicating action. In Europe, only anecdotical cases of Paederus sp. dermatitis have been reported. Since 1993, we have observed approximately 25 patients with suspected Paederus sp. dermatitis. In 9 the clinical diagnosis was confirmed because Paederus fuscipes were found. The case list includes 6 males and 3 females, ages ranging from 6 to 53 years (mean age: 26.3 years). Six patients presented with one lesion and 3 with 2 lesions. Eyelids (3 patients), shoulders (3), neck (2), cheek (1), breast (1), back (1) and calf (1) were involved. All patients showed erythema, 2 oedema, 2 blisters, 1 vesicles, 1 pustules and 1 crusts. In the patient with pustules, bacteriological examinations were negative. A biopsy was carried out in 4 patients. In the early stages, spongiosis with exocytosis of neutrophils was observed. Vesicles with neutrophils and necrosis of the epidermis were typical of the advanced stage. Oedema of the dermis and a mixed infiltrate, with eosinophils, neutrophils and lymphocytes, in the papillary and upper reticular dermis, were also observed. Direct immunofluorescencewas negative in all patients. Paederus sp. should also be considered in temperate climates as a possible aetiological agent in cases of acute dermatitis.