The term ectodermal dysplasias includes many disorders that share some clinical features such as involvement of one or several ectodermal structures and congenital origin. Currently, 154 different types divided into 11 clinical subgroups (Freire Maia classification 1994) have been described. The most frequent entity is hypo- or anhidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome). This is a rare hereditary disease whose main characteristic is the absence, or more often the reduction, of sweat glands, leading to an increase in body temperature together with anomalies of the epidermis and its appendages (hair and nails). We present a case of hypohidrotic ectodermal dysplasia in a premature 18-month-old boy who was referred to our department because of markedly dry skin since birth and recurrent eczematous and lichenification lesions that had been successfully treated with topical corticosteroids. Physical examination revealed mild alopecia with sparse and fine blonde hair and the absence of dental alveoli. The boy's mother had noticed slight sweating and episodes of fever without clinical symptoms, which were more frequent in summer. Hypohidrotic ectodermal dysplasia should be included in the differential diagnosis of fever of unknown origin.