SKIN March 2021 Volume 5 Issue 2 Copyright 2021 The National Society for Cutaneous Medicine 156 BRIEF ARTICLE A Case of Shiitake Mushroom Dermatitis in a 21-year-old Female Sheena T. Hill, MD, MPH1, Kord S. Honda, MD1, Bethany R. Rohr, MD1 1Department of Dermatology, University Hospitals Cleveland Medical Center, Cleveland, OH Shiitake mushroom dermatitis is a phenomenon that was first described in Japanese literature in 1977.1 Cases have now been reported throughout Europe, North America, and South America.2 It is a rare cutaneous reaction caused by consumption of raw or undercooked shiitake mushrooms (Lentinula edodes). Lentinan, a heat-inactivated β-glucan polysaccharide, is proposed to cause this dermatitis.3 Heat alters its structure, which is why this dermatitis is not seen with cooked shiitake mushrooms. To the authors’ knowledge, there have been few cases describing histologic findings of shiitake mushroom dermatitis. Here we present a case of shiitake mushroom dermatitis with correlation of histologic findings. A 21-year-old female presented with a five- day history of an extremely pruritic diffuse rash. She reported no new medications, products, preceding illness, or other notable positive review of systems, but did note cooking with shiitake mushrooms the day before onset of the rash. On physical examination, she had flagellate erythema on the posterior neck, arms, abdomen, bilateral flanks, and lower back, as well as scattered papules and vesicles (Figures 1-2). Figure 1. Shiitake mushroom dermatitis. Flagellate erythema of the right flank, where punch biopsy was performed. Figure 2. Shiitake mushroom dermatitis. Flagellate erythema of the neck, shoulders, and upper back. INTRODUCTION CASE PRESENTATION SKIN March 2021 Volume 5 Issue 2 Copyright 2021 The National Society for Cutaneous Medicine 157 A punch biopsy from the right flank was performed. Histopathologic evaluation revealed an interface dermatitis with focal parakeratosis, mild basal layer vacuolization, and a mild superficial perivascular lymphocytic infiltrate (Figures 3A and 3B). She noted improvement at two- week phone follow-up with use of triamcinolone 0.1% cream and shiitake mushroom avoidance. Figure 3. (A) Punch biopsy. Superficial perivascular lymphocytic infiltrate with mild basal layer vacuolization (H&E, 40x). (B) Punch biopsy. Higher magnification showing parakeratosis in an area of possible erosion with mild vacuolar alteration of basal keratinocytes and a superficial perivascular lymphocytic infiltrate (H&E, 100x). The exact pathophysiology of shiitake mushroom dermatitis is not well understood. It is thought that lentinan causes this dermatitis by a toxic or hypersensitivity reaction through activation of interleukin-1, thereby causing vasodilation and a rash.3,4 For those who favor a toxic mechanism, it is proposed that lentinan induces vasodilation and subsequent inflammation through interleukin.5,6,8,9 For those who favor a hypersensitivity mechanism, it is proposed that lentinan may cause a Th1 skew over Th2.3 Although there have been cases of positive patch testing in shiitake mushroom dermatitis, patch tests are usually negative due to poor antigen penetration.10,11 Patch tests are also not consistently positive in delayed food reactions.12 Because lentinan is thermolabile – inactivated at temperatures between 130 and 145 degrees Celsius due to irreversible molecular structure changes – shiitake mushroom dermatitis is not seen with well-cooked mushrooms.5 The histopathologic findings of flagellate erythema, specifically in shiitake mushroom dermatitis, are non-specific (Table 1). In a review of three flagellate erythema cases, histologic findings showed spongiosis and variable interface dermatitis with dermal lymphohistiocytic infiltrate.6,7 Eosinophils were prominent in two cases. In other case reports, histologic findings were variable and included hyperkeratosis, parakeratosis, dyskeratosis, spongiosis, and superficial mixed perivascular infiltrate with neutrophils, lymphocytes, and eosinophils.13-15 The clinical differential diagnosis in these cases should include bleomycin-induced flagellate hyperpigmentation, dermatomyositis, adult-onset Still disease, and acute contact dermatitis. ClinicalT DISCUSSION A. B. SKIN March 2021 Volume 5 Issue 2 Copyright 2021 The National Society for Cutaneous Medicine 158 Table 1. Literature review of histopathologic findings in flagellate erythema Case Sex Age (years) Histopathology Additional Findings Exposure Treatment Chu et al 20137 F 46 Superficial and mid-dermal perivascular mixed lymphocytic infiltrate with occasional eosinophils and neutrophils. Focal perivascular fibrin deposition. Normal ALT/AST, CBC with differential (including eosinophils) Chinese restaurant dish with reconstituted dried shiitake mushrooms Self-resolved after 4 weeks Chu et al 20137 M 46 Small foci of epidermal spongiosis with lymphocyte exocytosis. Superficial and mid- dermal perivascular and interstitial infiltrate of neutrophils, eosinophils, and mononuclear cells. -- Chinese restaurant dish with shiitake mushrooms Self-resolved after 3 weeks Corazza et al 20158 M 30 Intact epidermis, papillary dermal edema, erythrocyte overflow, superficial and perivascular mononuclear infiltrate without vasculitis or pigment incontinence -- Ate large amount of raw mushrooms five hours before onset of rash Self-resolved after 3 days Nakamura 19926 M 25 -- -- Ate salad with raw shiitake mushrooms Resolved in 10 days after treatment with antihistamine and topical steroids Soo et al 200715 M 58 Mild to moderate spongiosis with focal hyperkeratosis, mid- parakeratosis and minimal lymphocyte exocytosis. Mild perivascular lymphohistiocytic inflammatory infiltrate in superficial and mid-dermis. Normal CBC (including eosinophils), serum CK Chinese restaurant meal the night before Antihistamines and topical corticosteroids Hanada 199813 M 44 Intercellular edema, individual cell death, dermal edema, lymphocytic infiltrate, dilation of capillary vessels Negative ANA, normal porphyrins (urine, fecal, serum), normal CK, negative patch and photopatch tests 15-20 pieces of shiitake mushrooms daily for last 7 days Resolved in 7 days with antihistamines and topical corticosteroids M – Male; F-Female; ALT – alanine transaminase; AST – aspartate transaminase; CBC – complete blood count; CK – creatine kinase presentation differs in that pigmentation or hyperpigmentation is the main cutaneous finding in bleomycin-induced cases. In dermatomyositis, the rash is more inflammatory with persistent erythema and may be accompanied by photodistributed poikiloderma.1 Review of systems should include questions about myalgias, dysphagia, dyspnea, arrhythmias, and arthritis.1 In adult-onset Still disease, patients may report preceding sore throat, myalgias, or arthralgias, as well as recurrent fevers.1 In shiitake mushroom dermatitis, there are flagellate streaks made up of erythematous papules or vesicles, which may resolve with post-inflammatory SKIN March 2021 Volume 5 Issue 2 Copyright 2021 The National Society for Cutaneous Medicine 159 hyperpigmentation.1 Histopathology is not diagnostic and the diagnosis can be made clinically. Shiitake mushroom dermatitis typically self- resolves in one to eight weeks with avoidance of mushrooms. Patients are advised to thoroughly cook shiitake mushrooms prior to future consumption, which typically prevents recurrence. Symptomatic treatments include topical corticosteroids and oral antihistamines. Our patient improved with topical corticosteroids and mushroom avoidance. We present this case to highlight the importance of detailed history taking and to describe rarely reported histologic findings of shiitake mushroom dermatitis. Conflict of Interest Disclosures: None Funding: None Corresponding Author: Sheena T. Hill, MD, MPH Department of Dermatology University Hospitals Cleveland Medical Center 11100 Euclid Avenue Lakeside 3500 Cleveland, OH 44106 Phone: 216-844-8200 Fax: 216-844-8993 Email: Sheena.Hill@UHhospitals.org References: 1. Bolognia JL, Schaffer JV, Cerroni L, editors. Dermatology, 4th edition. China: Elsevier; 2018. p. 1129-1130. 2. Stephany MP, Chung S, Handler MZ, Handler NS, Handler GA, Schwartz RA. Shiitake Mushroom Dermatitis: A Review. Am J Clin Dermatol. 2016 Oct; 17(5):485-489. 3. Nguyen A, Gonzaga M, Lim V, Adler M, Mitkov M, Cappel M. Clinical features of shiitake dermatitis: a systematic review. Int J Dermatol. 2017; 56(6):610-616. 4. Hanada K, Hashimoto I. Flagellate Mushroom (Shiitake) Dermatitis and Photosensitivity. Dermatology 1998; 197(3):255-257. 5. Netchiporouk E, Pehr K, Ben-Soshan M, Billick RC, Sasseville D, Singer M. Pustular flagellate dermatitis after consumption of shiitake mushrooms. JAAD Case Rep. 2015 May; 1(3):117-119. 6. Nakamura T. Shiitake (Lentinus edodes) dermatitis. Contact Dermatitis 1992 Aug; 27(2):65-70. 7. Chu EY, Anand D, Dawn A, Elenitsas R, Adler DJ. Shiitake dermatitis. A report of 3 cases and review of the literature. Cutis 2013;91:287-290. 8. Corazza M, Zauli S, Ricci M, Borghi A, Pedriali M, Mantovani L, Virgili A. Shiitake dermatitis: toxic or allergic reaction? J Eur Acad Dermatol Venereol. 2015 Jul; 29(7):1449-1451. 9. Tan Q, Tan C. Log-grown shiitake is perhaps the real cause for Shiitake dermatitis. J Eur Acad Dermatol Venereol. 2016 Jan; 30(1):197-198. 10. Ching D, Wood BA, Tiwari S, Chan J, Harvey NT. Histological features of flagellate erythema. Am J Dermatopathol. 2019 Jun; 41(6):410-421. 11. Kopp T, Mastan P, Mothes N, Tzaneva S, Stingl G, Tanew A. Systemic allergic contact dermatitis due to consumption of raw shiitake mushroom. Clin Exp Dermatol. 2009;34:e910-913. 12. Sutas Y, Kekki OM, Isolauri E. Late onset reactions to oral food challenge are linked to low serum interleukin-10 concentrations in patients with atopic dermatitis and food allergy. Clin Exp Allergy. 2000;30:1121-1128. 13. Hanada K, Hashimoto I. Flagellate mushroom (shiitake) dermatitis and photosensitivity. Dermatology. 1998;197: 255-257. 14. Lippert U, Martin V, Schwertfeger C, et al. Shiitake dermatitis. Br J Dermatol. 2003;148: 178-179. 15. Soo JK, Pearson IC, MIsch KJ. A case of flagellation. Clin Exp Dermatol. 2007;32: 339- 340. CONCLUSION mailto:Sheena.Hill@UHhospitals.org