What is undifferentiated connective tissue disease in lay man's terms?

Mixture of many: It is a mixture of findings from a variety connective tissue diseases including systemic lupus erythematosus, rheumatoid arthritis, polymyositis and scleroderma. One does not have allof the symptoms at one time but can overlap from one to another with arthritis, rashes, internal involvement of lungs, heart, kidney less often.

See details: It is a disorder with features of a connective tissue disease but not enough clinical data to say for sure what specific disease it is. Personally, i doubt that this disorder exists. The overwhelming majority of patient i see with this diagnosis turn out to have lupus.