Flagellate erythema: from diet, drugs to dermatomyositis

A fit 75‐year‐old man presented with a one‐day history of a widespread flagellate‐patterned asymptomatic eruption involving the neck, trunk and upper arms (Figure). He had ingested undercooked shiitake mushrooms 48‐hours prior. The eruption resolved within a week with oral prednisolone 0.5 mg/kg/day prescribed for a faster recovery, which would otherwise occur spontaneously within 1–8 weeks. He was warned to avoid ingesting shiitake mushrooms again, although thorough cooking would likely prevent recurrence of the eruption. Flagellate erythema is a unique sign that can occur secondary to the 3Ds: diet (undercooked shiitake mushrooms), drugs (bleomycin/docetaxel), and more serious rheumatological conditions, such as dermatomyositis or adult‐onset Still's disease.