A 63-year-old man with diabetes, hypertension, and dyslipidemia came to the emergency department with slightly pruritic skin lesions that had appeared 48hours earlier. He denied having taken any new or different medications. However, when asked about foods, he reported eating shitake mushrooms 2 days before the lesions appeared. He also had a 2-month history of muscle pain in both shoulders, but mainly on the right, and with no weakness in either the shoulder or pelvic girdle. Physical examination revealed multiple lesions consisting of erythematous–violaceous papules distributed on the chest, buttocks, and lower extremities arranged in groups of 5or 6 parallel lines of differing lengths, resembling lash marks (Figs. 1A and 1B). The patient denied scratching, and a dermographism test was negative. Suspecting an amyopathic or hypomyopathic dermatomyositis, which can lead to rapidly progressing lung involvement, we ordered a chest radiograph and a blood work-up for creatine phosphokinase, aldolase, lactate dehydrogenase, myositis-specific autoantibodies (anti-tRNA synthetase, anti-Mi-2, anti-SRP, anti-Ku, anti-PM/Scl, and anti-U1RNP) and anti-MDA5 and anti-p155/140 autoantibodies. All results were within rigorously normal limits. The lesions had nearly cleared a week later and itching could be controlled with oral antihistamines. Flagellate erythema due to shitake mushrooms was diagnosed and no further tests were ordered. The patient has remained free of symptoms and lesions for 6 months.

Figure 1

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