What is an overlap syndrome?

Many patients diagnosed with autoimmune rheumatic disease display overlapping features of different connective tissue diseases and cannot be categorized easily into one of the established clinical entities, such as systemic lupus erythematosus, dermatomyositis, or systemic sclerosis. The term “overlap syndrome” has been used to classify these patients and is useful for descriptive purposes, clarifying prognosis and facilitating disease management.