Shiitake dermatitis demonstrating Köebner phenomenon

Abstract

Shiitake mushroom (Lentinus edodes) ingestion can induce a clinically distinctive dermatitis. Most cases have appeared in Japan and, recently, in Europe. We describe a patient from the United States who developed shiitake dermatitis and demonstrated k€ oebnerization on rechallenge. Case historyA 28-year-old man presented with a 1-day history of an extensive pruritic linear rash. He had eaten four to five steam-cooked shiitake mushrooms (originally dried) approximately 10 hours before rash onset. He had eaten shiitake mushrooms two weeks before without development of a rash. On exam, he had erythematous, edematous linear plaques on his trunk, upper extremities, and neck ( Fig. 1). Based on clinical findings, he was diagnosed with shiitake flagellate dermatitis. The patient's rash resolved in one week with a prednisone taper (40 mg for four days and taper by 10 mg every four days thereafter) and topical clobetasol. No antihistamines were given.Six months later, he underwent rechallenge with two raw shiitake mushrooms. DuoDerm â patches were placed on his right flank to prevent scratching in an area where lesions had been present during the initial outbreak. Four hours after ingesting the mushrooms, he experienced flushing and generalized pruritus (without rash) that resolved in two hours. He wrote his initials on his left flank with his finger during this pruritic period. Approximately 44 hours after eating the mushrooms, he developed a pruritic rash in the area where he had written his initials (Fig. 2). Additionally, erythematous, edematous linear plaques were present on the upper back, chest, shoulders, and neck. No lesions were present under the DuoDerm â on his right flank (Fig. 1). Two lesional punch biopsies were obtained; one was from within a k€ oebnerized initial area, the other from a flagellate erythematous plaque on the right shoulder.Both biopsies demonstrated superficial perivascular lymphocytic infiltrates with occasional eosinophils. The infiltrate in the deliberately k€ oebnerized lesion extended into the mid-dermis. The other biopsy also showed mild acanthosis and spongiosis with focal lymphocyte exocytosis. Recurrent rash was also treated successfully with identical prednisone taper and topical clobetasol.Several weeks later, he agreed to eat fully cooked shiitake mushrooms. Neither rash nor pruritus developed. Discussion

Clinical features of shiitake dermatitis: a systematic review

“…Conversely, the fact that this rash usually occurs after the ingestion of large amounts of raw mushroom and not after limited exposures suggests that there may be a dose‐dependent effect, which is consistent with a toxic mechanism . However, we favor a hypersensitivity reaction and postulate that genetically susceptible individuals with certain human leukocyte antigen (HLA) alleles require exposure to large amounts of lentinan in order to be sensitized.…”

“…All included cases resulted after the oral consumption of shiitake mushroom in various forms, including raw ( n = 26) and lightly or undercooked (including in soups and stir fries, n = 10). In three cases, the subjects had not experienced any reactions to the consumption of shiitake mushrooms prior to the reported incident: one case had previously consumed roasted mushrooms, and another reported no reaction after consuming shiitake mushrooms as recently as 2 weeks previously . Two cases reported recurring symptoms before diagnosis (at 1 year and 16 years, respectively) .…”

“…). Twenty‐nine articles were included, comprising a total of 50 cases of patients with shiitake dermatitis . Articles consisted of case reports (24 patients) and case series (26 patients).…”

“…The distribution of linear, flagellate papules and vesicles is likely to be Koebner‐induced, a phenomenon characterized by the reproduction of lesions after trauma to the skin. Although some reports were unable to reproduce lesions by scratching, Ade et al . were able to clearly demonstrate the cutaneous reproduction of patients' initials 44 h after rechallenge with mushrooms, without the involvement of protected skin.…”

“…Some authors claim that lentinan produces a predictable and dose‐dependent response, representing a toxic mechanism, whereas others postulate an unpredictable, immune‐mediated response, occurring in genetically predisposed individuals, independently of dose, representing a hypersensitivity mechanism . In support of the hypersensitivity theory, Corazza et al .…”