Objectives: To investigate the rate of disease evolution in a cohort of patients with undifferentiated connective tissue disease (UCTD) and to determine clinical and immunological features more frequently associated with disease progression.
Methods: This retrospective single-centre long-term follow-up cohort study included patients with UCTD diagnosis, ANA positive, with a follow-up of at least 2 years.
Results: A total of 100 UCTD patients were recruited. During the follow-up (6.2±2.1 years), 44 patients (44%) developed novel clinical and/or laboratory features (rate of development patient/year of 7%), and 21 patients (21%) evolved into a definite connective tissue disease (CTD) after a mean time of 7±5.5 years with a rate of disease evolution (patient/year) of 3%. New clinical manifestations (39 patients) included: joints (36%), haematological (30%), cutaneous (13%), pulmonary (10%) and renal (10%) involvement. New laboratory findings (17 patients (17%)) included: 2 anti-ENA positivity, 3 anti-dsDNA antibodies positivity and 6 low complement levels. At follow-up, 13 patients (61.9%) met the classification criteria for systemic lupus erythematosus, 1 patient (4.8%) for mixed CTD, 5 patients (23.8%) for systemic sclerosis and 2 patients (9.5%) for Sjögren's syndrome. Patients evolving towards a new diagnosis had longer disease duration (15.2±9.7 years vs. 10±5.8 years; respectively, p<0.005), had a higher prevalence of anti-Ro/SSA antibodies (63.2% vs. 28.4%; respectively, p<0.05) and anti-RNP antibodies (21.1% vs. 7.4%; respectively, p<0.05). The statistical difference was also confirmed after the multivariate analysis.
Conclusions: Up to 45% of UCTD patients might develop novel clinical and/or laboratory features during the follow-up, leading to evolution into a definite CTD in 1 out 5 cases.