Background The diagnosis of Undifferentiated Connective Tissue Disease (UCTD) has raised controversy over the years regarding making the diagnosis, evolution and prognosis. Le Roy et al^[1] in 1980 and most recently Mosca et al^[2] in 2014 proposed classification criteria for UCTD, but confusion still exists regarding making the diagnosis of UCTD, evolution and prognosis of the syndrome and how the patient should be followed up over time.

Objectives Evaluate disease evolution, treatment and follow up plan in patients with UCTD diagnosis. Assess whether there are any factors that may predict disease evolution and should require regular follow up.

Methods This was a retrospective study of patients followed up in a specialist clinic in a tertiary referral centre (University College London Hospitals) with a diagnosis of UCTD, focusing on clinical and serological features, treatment, follow up and disease evolution over time.

Results A total of 121 patients were included in the study: 93% were females; the mean age at disease onset was 39 years (range 20 to 80); and the patients were followed up for at least 1 year (mean 12 years, range 1 to 40). 78% of these patients had a stable diagnosis of UCTD, while in 22% diagnosis changed over time: 9% evolved into a specific connective tissue disease (CTD) - 4 Systemic Lupus Erythematosus, 3 Sjogren's Syndrome, 1 Rheumatoid Arthritis, 1 Systemic sclerosis and 1 Anti-synthetase Syndrome -, 7% had a change of diagnosis from a specific CTD to UCTD, 4% evolved into an overlap syndrome and 2% of the patients were no longer diagnosed as having any CTD at the end of the study. The most prevalent manifestations were joint pain (arthralgia/arthritis) in 89% of the patients, fatigue 80%, Raynaud's phenomenon 63%, skin rashes 49% and sicca symptoms 45%. Lung involvement was observed in 11% of the patients within which 8% had a nonspecific interstitial pneumonia (NSIP) and 3% had a usual interstitial pneumonia (UIP) pattern. 36% of the patients were noted to have associated gastro-oesophageal reflux disease. Serological features included positive ANA in 98%, anti-RNP 33%, anti-Ro 32%, Rheumatoid Factor 20% and hypocomplementemia was observed in 19% of the patients. 7% of the patients did not require any treatment for their UCTD, but the majority of patients were treated with Hydroxychloroquine only (75%), and the rest with other immunosupressants/immunomodulators.

Conclusions In our study the majority of patients initially diagnosed with UCTD kept this diagnosis over time but 13% of patients evolved to a defined CTD or an overlap syndrome and in 2% of patients, symptoms and serological features eventually resolved. Although, UCTD is often mild, significant major organ involvement such as interstitial lung disease can occur^[3], as well as evolution to a defined CTD or overlap syndrome. This should guide follow up of these patients in clinic.

1. LeRoy EC et al. Undifferentiated connective tissue syndromes. Arthritis Rheum.1980; 23 (3):341 - 343.

2. M. Mosca et al The diagnosis and classification of undifferentiated connective tissue diseases Journal of Autoimmunity 48–49 (2014) 50e52.

3. Fischer A, Interstitial lung disease in undifferentiated forms of connective tissue disease. Arthritis Care Res (Hoboken). 015;67(1):4–11.

Disclosure of Interest R. Ionescu Grant/research support from: EULAR scientific training bursary, M. Leandro: None declared