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November 15, 2010

Flagellate Dermatitis—Diagnosis

Author Affiliations


Arch Dermatol. 2010;146(11):1301-1306. doi:10.1001/archdermatol.2010.321-b

Histologic examination revealed the features of an acute dermatitis with edema in the papillary dermis and a dermal perivascular cell infiltrate of lymphocytes and histiocytes. The patient was treated with antihistamines and potent topical corticosteroids. The eruption resolved within 10 days, leaving no pigmentary change.

Shiitake mushrooms (Lentinula edodes) are the second most commonly cultivated mushroom in the world after button mushrooms (Agaricus bisporus). Inhalation of shiitake spores has been reported to cause allergic alveolitis or bronchial asthma in workers involved in cultivating or marketing this mushroom. Shiitake dermatitis was first described in Japan1 and was termed toxicoderma. It is more commonly reported in the literature by Japanese authors2 and is less known in the western world.3 It typically occurs 1 to 2 days after eating raw or half-cooked shiitake mushrooms. Characteristic skin manifestations2 include small erythematous papules in a linear pattern on the trunk and extremities and sometimes on the face. Pruritus is a strong feature, but there is no mucosal involvement. The eruption actually spares the back in areas the patient cannot reach, suggesting that a component of the eruption could be attributable to scratching. A photosensitive reaction has been seen in 47% of patients reviewed with shiitake dermatitis.4 Diagnosis is based on the dietary history and distinctive eruption. Findings from skin biopsies are nonspecific and show features such as spongiosis; elongation of rete ridges; and a perivascular cell infiltrate of lymphocytes, neutrophils, and eosinophils.2 Oral challenge test may confirm the diagnosis. Patch testing and skin prick test are inappropriate because this is not an allergic phenomenon. The underlying pathogenesis is thought to be a toxic reaction to lentinan, a thermolabile mushroom polysaccharide that has been found to have antitumor properties5 and is used as an adjunctive treatment for colorectal and gastric malignant diseases in Japan. When it was used as a chemotherapy agent in Japan, cutaneous manifestations resembled that of shiitake dermatitis, supporting its pathogenic role.6 Flagellate dermatitis is also well recognized in association with bleomycin sulfate usage, which is seen in around 20% of patients who receive this drug.7 The exact pathogenesis is again unknown but is thought to be due to its sulfur component. The characteristic flagellate linear groups of erythematous vesicular or urticarial lesions may occur from a few hours to 9 weeks after administration of the drug. However, unlike shiitake dermatitis, stomatis is common, and skin hyperpigmentation occurs.8 Shiitake mushrooms are widely available in supermarkets in Europe, but to our knowledge, this is the first reported case of shiitake dermatitis in France.

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