The connective tissue diseases are a family of closely related disorders. They include: rheumatoid arthritis (RA), systemic lupus erythematosus (SLE or lupus), polymyositis-dermatomyositis (PM-DM), systemic sclerosis (SSc or scleroderma), Sjogren's syndrome (SS) and various forms of vasculitis.
These diseases have a number of common features
They affect women much more frequently than men.
They are "multisystem" diseases, capable of affecting the function of many organs.
They "overlap" with one another, sharing certain clinical symptoms, signs, and laboratory abnormalities.
Blood vessels are the most common target of injury in all of these diseases.
The immune system is abnormal and accounts, at least in part, for the observed tissue damage.
Although lupus most often occurs alone, many people with lupus also have symptoms characteristic of one or more of the other connective tissue diseases. In this circumstance, a physician may use the term "overlap" to describe the illness. There are several well-recognized overlaps that may affect people with lupus.