SHIITAKE DERMATITIS (FLAGELLATE MUSHROOM DERMATITIS)
Synonyms: Shiitake mushroom dermatitis Lentinan dermatitis Shiitake-induced toxicoderma
Key features
Occurs after eating large amounts of raw or partially cooked shiitake mushrooms
Flagellate streaks initially composed of erythematous papules or petechiae develop on the face, trunk, and extremities
Introduction
Shiitake dermatitis occurs in individuals who have ingested raw or undercooked shiitake mushrooms (Lentinula edodes). It presents with linear streaks of erythematous papules or petechiae, which occasionally evolve to flagellate pigmentation similar to that induced by bleomycin. Of note, occupational skin and respiratory conditions can develop in workers who cultivate shiitake mushrooms, with manifestations including protein contact dermatitis and hypersensitivity pneumonitis (“mushroom worker’s disease”).
History and Epidemiology
Toxicoderma caused by shiitake mushroom ingestion was first described in the Japanese literature in 1977. Since then, several hundred cases of “shiitake dermatitis” have been reported, initially mostly from Japan and Europe but nowadays globally due to the widespread popularity of East Asian cuisines. Similar eruptions due to ingestion of wood ear (Auricularia auricula-judae) or porcini (Boletus spp.) mushrooms have also been described.
Pathogenesis
Lentinan, a thermolabile toxin in shiitake mushrooms, is probably responsible for this dermatosis. Prick and patch tests using shiitake mushroom extract are typically negative in patients who have ingestionrelated dermatitis, and oral rechallenge may be negative as well. A phototoxic mechanism has also been proposed.
Clinical Features
In shiitake mushroom dermatitis, pruritic erythematous papules, vesicles, and edema develop on the face, scalp, trunk, and extremities 1–2 days after mushroom ingestion. Scratching leads to long, flagellate streaks composed of erythematous papules and/or petechiae on the extremities and the trunk, with sparing of the difficult-to-reach mid upper back. This can be followed by a linear pattern of either discoloration due to hemosiderin or PIH. Diffuse erythema and edema in photo-exposed areas have been observed in half of Japanese patients with shiitake dermatitis, and fever and malaise are occasional associated findings.
Pathology
Spongiosis and necrotic keratinocytes are seen within the epidermis in addition to a lymphocytic dermal infiltrate, which is admixed with melanophages in cases with hyperpigmentation.
Treatment
The acute dermatitis can be treated with topical corticosteroids and oral antihistamines. Resolution occurs within 1 to 8 weeks if the mushrooms are avoided. Thoroughly cooking shiitake mushrooms prevents the disorder.