Disease evolution and organ damage accrual in patients with stable UCTD: a long-term monocentric inception cohort

Objectives Undifferentiated connective tissue diseases (UCTDs) are systemic autoimmune conditions that cannot be diagnosed nor classified as defined CTD; the majority maintains an undifferentiated profile (stable UCTD, sUCTD) over time. Data on long-term outcomes of sUCTD are lacking. Methods Retrospective longitudinal analysis of an inception cohort of 141 patients with sUCTD. Disease evolution and damage accrual were evaluated at 1, 5 and 10 years. Partial least square (PLS) regression was used to identify the basal variables contributing to damage accrual at 1, 5 and 10 years of follow-up. Trend of damage over time was compared with a cohort of age-matched and sex-matched patients with systemic lupus erythematosus (SLE) by means of Nelson-Aalen analysis. Results 11.3% of patients evolved to a definite CTD after a median 11 years (IQR 6–25) from the first symptom. At last visit, 10% were on glucocorticoids and 6% on immunosuppressive therapy. In 27.3%, at least one item of organ damage was recorded according to the SLICC/DI score (mean score 1.19±0.46). At PLS analysis, age at diagnosis and age at first symptoms were related to damage at 1 year, not taking antimalarials and taking immunosuppressants were associated with damage at 5 years. The mean survival without damage was 9.3 years in sUCTD and 8.4 years in SLE. The 10-year probability without damage was 62% and 23% in SLE and sUCTD, respectively (p=0.015). Conclusions Although less significantly impacted than in patients with SLE, in the long-term UCTDs can accumulate organ damage and evolve into defined connective tissue diseases. Data are available on reasonable request. The data that support the findings of this study are available on request from the corresponding author on reasonable request.