Shiitake Dermatitis: First Report From Turkey

A 54-year-old male patient presented with complaints of itching, redness, and swelling that had been present for two days. His general condition was good, and he had no systemic complaints. The patient had previously consulted a doctor twice with a similar rash and recovered in a short time. He had a history of hypertension and use of anti-hypertensive drugs. Dermatological examination showed wheals with a linear, flagellate appearance, concentrated on the neck and trunk, involving the upper extremities (Figure 1) and face. There was no mucosal involvement. In the punch biopsy specimen, a spongiotic dermatitis with marked papillary dermal oedema and some eosinophils was observed (Figure 2). When questioned, the patient stated that he liked eating and trying different types of mushrooms and Asian foods. He had also travelled to Japan thirteen times for business reasons. The day before the onset of the rash, he had consumed soup containing shiitake mushrooms at a Japanese restaurant in Turkey. With these clinical and pathological findings, the patient was diagnosed with shiitake dermatitis. It regressed in 3 days with topical steroid and antihistamine treatment.

Shiitake dermatitis is a self-limiting condition presenting with typical flagellate erythema that begins approximately 1–2 days after consumption of undercooked or uncooked shiitake mushrooms. Its pathogenesis is not clear. It is thought to be a toxidermia caused by the thermolabile polysaccharide component called lentinan found in the fungal cell wall. Some authors think that it is a hypersensitivity reaction seen in people with a genetic predisposition. Skin tests such as patch tests and prick tests were found to be positive in some patients and negative in others, and their results are contradictory [1]. This Turkish patient's frequent travels to Japan and consumption of Asian cuisine suggested that there may be an individual upper limit threshold in the mechanism of formation of this dermatitis, and it may occur with cumulative toxicity.

Differential diagnosis of linear/flagellate pruritic papules includes dermatographic urticaria, chemotherapy-associated flagellate erythema, dermatomyositis-associated flagellate erythema, adult-onset Still's Disease, and photophytodermatitis. In dermographism, the lesions are transient and short-lived. In flagellate erythema associated with chemotherapy, there is a drug history. Dermatomyositis can be distinguished by laboratory findings. In Shiitake dermatitis, there are no systemic symptoms as in adult-onset Still's Disease. In photophytodermatitis, there is a contact history.

Shiitake mushroom (Lentinula edodes) is the second most frequently consumed mushroom species in the world [2]. Due to the spread of East Asian cuisine culture in many countries, the number of countries where shiitake dermatitis is seen is increasing [3]. This case is the first case reported from Turkey. It is presented to remind of shiitake dermatitis in the differential diagnosis of flagellate erythema. Mushroom consumption history is an important clue for diagnosis.

Ceyda Çaytemel: conceptualization, investigation, writing – original draft, visualization, writing – review and editing. Cüyan Demirkesen: conceptualization, writing – review and editing, visualization, supervision.

The patient has signed a written formal consent to the publication of medical history and clinical picture.

The authors declare no conflicts of interest.