AbstractTwo siblings, a 38‐year‐old woman and a 33‐year‐old man, developed eosinophilic fasciitis within a period of 6 months. They were found to have identical HLA–A, B, DR, and DQ antigens, raising the possibility of a genetic influence in the development of this disease. No common environmental factors close to the time of onset were identified; however, the possibility of a common, remote environmental factor cannot be discounted.