Undifferentiated Connective Tissue Disease (UCTD) is a chronic autoimmune condition characterized by signs and symptoms of connective tissue diseases—such as lupus, scleroderma, or Sjögren’s syndrome—without meeting the full criteria for a specific diagnosis. It involves immune system dysfunction that causes inflammation in joints, skin, muscles, or other tissues. UCTD may remain stable, evolve into a defined autoimmune disease, or even resolve spontaneously.