Risk of Cancer in Dermatomyositis or Polymyositis

To the Editor: Sigurgeirsson et al. (Feb. 6 issue) 1 used what must now be regarded as unacceptable criteria to distinguish between polymyositis and dermatomyositis. It is very likely that some of their patients classified as having polymyositis in fact had dermatomyositis, and the question of whether there is an increased risk of cancer among patients with polymyositis therefore remains unanswered. The available evidence does strongly indicate a link between dermatomyositis and cancer. The criteria they used require the presence of a rash to distinguish between dermatomyositis and polymyositis. 2 These criteria were established at a time when dermatomyositis and polymyositis were . . .