A 33-year-old man with ectodermal dysplasia (ED) has suffered from keratotic, exudative, erythematous plaques on the genital area, thighs, and soles since age 17. Verrucous soft nodules in a cobblestone arrangement developed on the erythematous plaque on his left thigh when he was 31 years old. Histologic examination of the verrucous nodules demonstrated that they were composed of anastomosing thin cords of uniform, cuboidal, epithelial cells and a fibrovascular stroma. The changes are indicative of eccrine syringofibroadenoma of Mascaro (ESFA), which has been reported as a neoplasm, a hamartoma, or a nevus. With etretinate treatment, the verrucous nodules completely disappeared within two months. Similar, but much flatter, verrucous lesions recurred and disappeared twice during the subsequent two years period. These verrucous lesions were likely induced by irritation from urine, stool, and/or mechanical friction. This case of ESFA in a patient with ED clearly showed a reactive process which was successfully managed with oral etretinate.