Undifferentiated Connective Tissue Disease, Mixed Connective Tissue Disease, and Overlap Syndromes in Rheumatology.

Autoimmune diseases often have overlapping symptoms and laboratory somewhat unfamiliar to the non-rheumatologist. Characteristic signs, symptoms, and autoantibodies define specific connective tissue diseases. Some patients have some characteristic symptoms, but cannot be definitively classified. Still other patients meet criteria for more than one specific connective tissue disease. These patients can be confusing with regard to diagnosis and prognosis. Clarification of each patient's condition can lead to improved patient care.