A 16-year-old boy had the skin changes of poikiloderma atrophicans vasculare, limited to one arm. None of the conditions recognized as being associated with poikiloderma was present. Subsequent investigation showed that he suffered from a genetically determined form of muscular dystrophy as well as a possible incomplete form of Marfan's syndrome. To our knowledge, this is the first report of poikiloderma being associated with either disease.