How common is undifferentiated connective tissue disease?
About 25% of patients presenting to rheumatologists may not fulfill criteria for a defined connective tissue disease at the time of presentation.
Over time (1–3 years), about 25% of these patients will evolve into a defined rheumatologic diagnosis.
The majority of patients with undifferentiated connective tissue disease are female (80%–95%) with disease onset during the fourth decade (30–40 years).
