Mixed connective tissue disease has signs and symptoms of a combination of disorders — primarily lupus, scleroderma and polymyositis. For this reason, mixed connective tissue disease is sometimes referred to as an overlap disease. MCTD combines features of scleroderma, myositis, systemic lupus erythematosus, and rheumatoid arthritis (with some sources adding polymyositis) and is thus considered an overlap syndrome.
In mixed connective tissue disease, the symptoms of the separate diseases usually don't appear all at once. Instead, they tend to occur in sequence over a number of years, which can make diagnosis more complicated. Early signs and symptoms often involve the hands. Fingers might swell like sausages, and the fingertips become white and numb. In later stages, some organs — such as the lungs, heart and kidneys — may be affected.
The average age of onset is 37 years. Approximately 80 percent of individuals are female.MCTD occurs worldwide and in all races, with a peak incidence in the teens and 20s. About 80% of people who have this disease are women. The cause is unknown. In some patients, the disorder evolves into classic systemic sclerosis or SLE.