Unravelling IPAF, VEDOSS and connective tissue diseases classifications through the mixed connective tissue disease...

Mixed connective tissue disease (MCTD) has long been debated as an early nonspecific phase/symptom of differentiated connective tissue diseases (dCTD), similarly to interstitial pneumonia with autoimmune features (IPAF) and very early diagnosis of systemic sclerosis (SSc) (VEDOSS).

We aimed to evaluate the predictive value of IPAF, VEDOSS and dCTD classification criteria variables in MCTD patients.

We conducted an observational study within the French MCTD cohort. IPAF, VEDOSS and current dCTD classification criteria were used to classify patients.

Three hundred and twenty-four MCTD patients were included and followed for 8 (3.3-13) years. Among them, 111 (34.3%) progressed into a dCTD, that is, 50 (15.4%) SSc, 40 (12.3%) systemic lupus erythematosus (SLE) and 11 (3.4%) Sjögren's disease. At diagnosis, 38 (11.7%) patients fulfilled IPAF criteria, among which 15 (39.5%) progressed into a dCTD (vs 75 (26.2%) in patients who did not fulfil IPAF criteria; p=0.09). At diagnosis, 293 (90.4%) patients fulfilled VEDOSS criteria but did not progress significantly more frequently to SSc than MCTD patients without VEDOSS criteria (46 (15.7%) vs 4 (12.9%); p=0.8). At baseline, SSc classification criteria did not predict evolution toward SSc, whereas antiphospholipid antibodies and low C3 and/or C4 were predictive of an evolution toward SLE (p=0.01 and p=0.04, respectively).

At MCTD diagnosis, fulfilment of IPAF and/or VEDOSS criteria was not predictive of evolution toward SSc, whereas antiphospholipid antibodies and low C3 and/or C4 were predictive of an evolution toward SLE. This suggests that MCTD patients should be excluded from IPAF and VEDOSS.