<prompt> Answer this question truthfullyWhat does Undifferentiated: connective tissue disease mean?  <response>: <reason> The symptoms of undifferentiated connective tissue disease UCTD usually are similar to connective tissue diseases but couldnt complete the criteria for their definitive diagnosis. If left untreated, 24.3-33 of patients with UCTD may progress to develop manifestations of well defined connective tissue disease such as systemic lupus erythematosus, rheumatoid arthritis, Sjögrens syndrome. Common complications of UCTD include Interstitial lung disease - Non specific interstitial pneumonia, atherosclerosis. Depending on the extent of the UCTD at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good. The presence of interstitial lung disease is associated with a particularly good prognosis among patients with UCTD rather than being idiopathic. 