Background:Eccrine angiomatous hamartoma is a rare benign cutaneous malformation with a diverse clinical appearance, therefore likely to be misdiagnosed and underreported.Main observations:A 44-year-old man presented with a congenital erythematous hyperhidrotic plaque on the left upper back measuring 18 x 25 cm. No pain or tenderness nor hypertrichosis were observed. Histopathology was consistent with the mucinous variant of eccrine angiomatous hamartoma. Intralesional injection of botulinum toxin type A greatly reduced localized sweating, improving patient quality of life.Conclusions:This article describes a novel clinical presentation of eccrine angiomatous hamartoma: large, erythematous, and slightly indurated plaque localized on the upper back. It emphasizes the role of histopathology in the diagnostic process and botulinum toxin as a viable treatment option.