Secondary Sjögren's syndrome--the sausage factory revisited.

Many different factors combined cause an autoimmune disease like Sjögren's syndrome. In this review a new analogy is described to represent the relationship between Sjögren's when it occurs on its own, compared to its existence against the background of another autoimmune condition. The issue of whether Sjögren's should really be thought of as a syndrome or a disease is also highlighted.