Mixed Connective Tissue Disease (MCTD) and Undifferentiated Connective Tissue Disease (UCTD)

In Mixed Connective Tissue Disease (MCTD), features of various connective tissue disorders such as systemic lupus erythematosus (SLE), systemic sclerosis (PSSc), dermatomyositis/polymyositis (DM/PM), and occasionally Sjogren's syndrome and rheumatoid arthritis (RA) can coexist and overlap. The picture is marked by the presence of high titer anti-U1 ribonucleoprotein (RNP) antibodies. Over the last 30 years since first described a lot of controversial studies have been published regarding the nature, the severity or the very existence of the condition. We review here the various aspects and the characteristics which make it a distinctive autoimmune condition. We discuss the new understanding of the prognosis of this connective tissue disorder. We give an update on the management of MCTD. Some aspects of the Undifferentiated Connective Tissue Disease (UCTD) are approached as a class apart.