| Shiitake mushroom dermatitis | |
|---|---|
| Other names | Flagellate mushroom dermatitis, Mushroom worker's disease, and Shiitake-induced toxicoderma. [1] |
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| Symptoms on back and leg. Stripes appear when skin is scratched or spontaneously in friction or contact zones. | |
| Specialty | Dermatology |
Shiitake mushroom dermatitis is an intensely itchy dermatitis characterized by disseminated 1mm erythematous micropapules seen in a linear grouped arrangement secondary to Koebnerization due to patient scratching. [1] It is caused by the ingestion of shiitake mushrooms and was first described in 1977 by Nakamura. [2] Although it is rarely seen outside China and Japan due to a lower incidence of shiitake consumption outside these regions, there is a well-established association between flagellate dermatitis and shiitake mushroom (Lentinula edodes) ingestion. Bleomycin ingestion may also cause similar findings. On physical exam, one key difference between the two is that post-inflammatory hyperpigmentation changes are usually seen with bleomycin-induced flagellate dermatitis and are not typically present with shiitake mushroom induced flagellate dermatitis. [3] The median time of onset from ingestion of shiitake mushrooms is typically 24 hours, ranging from 12 hours to 5 days. Most patients completely recover by 3 weeks, with or without treatment. [4] Although the pathogenesis of shiitake induced flagellate dermatitis is not clear, the theory most argued for is a toxic reaction to lentinan, a polysaccharide isolated from shiitake mushrooms. [2] However, Type I and Type IV allergic hypersensitivities have also been supported by the 24-hour median time of onset, clearance in 3–21 days, severe pruritus, benefit of steroids and antihistamines, and lack of grouped outbreaks in people exposed to shared meals containing shiitake mushrooms. [2] [4] Most cases reported shortly after its discovery were due to consumption of raw shiitake mushrooms, but several cases have since been reported after consumption of fully cooked mushrooms. [3]
