Overlap syndrome

Overlap syndrome refers to the overlap between two or more connective tissue diseases, also known as overlapping connective tissue disease. This overlap can occur at the same time, so that the patient meets the diagnosis of two or more connective tissue diseases at the same time; another connective tissue disease may occur at different times; or a connective tissue disease first, and later Transition to another CTD. This transition can occur continuously or after a certain period of time. OS usually occurs in the overlap of 6 diffuse CTDs, namely SLE, RA, DM / PM, PSS, nodular polyarteritis (PN) and rheumatic fever (RF). It can also be caused by 6 CTDs and related diseases such as white The disease overlaps with Sjogren's disease, Sjögren's syndrome, and panniculitis. In addition, it can overlap with other autoimmune diseases such as chronic thyroiditis, autoimmune hemolytic anemia, and so on.