ObjectivesPatients with incomplete systemic lupus erythematosus (iSLE) have lupus features, but do not meet classification criteria for SLE. Type I interferons (IFN) are important early mediators in SLE, and IFN upregulation in incomplete SLE may be associated with progression to SLE. Since many patients present with skin symptoms, the aim of this study is to investigate IFN type I expression and IFN-related mediators in the blood and skin of iSLE patients.MethodsTwenty-nine iSLE patients (ANA titer ≥ 1:80, symptoms < 5 years, ≥ 1 objectified clinical criterion), 39 SLE patients with quiescent disease (fulfilling ACR or SLICC criteria, SLEDAI ≤4), and 22 healthy controls were included. IFN signature was measured in whole blood, based on 12 IFN-related genes, using RT-PCR, and IFN-score was calculated. IFN-related mediators myxovirus-resistance protein A (MxA), IFN-γ-induced protein 10 (IP-10), and monocyte chemoattractant protein (MCP-1) were measured using ELISA. IFN type I expression in the unaffected skin was analyzed by immunostaining with MxA.ResultsIFN-score was increased in 50% of iSLE patients and 46% of SLE patients and correlated positively with the number of autoantibodies, anti-SSA titer, ESR, and IgG and negatively with C4 in iSLE. Levels of MxA correlated strongly with IFN-score (r = 0.78, p < 0.0001). Furthermore, MxA expression was found in 29% of unaffected skin biopsies of iSLE and 31% of SLE patients and also correlated with IFN-score (r = 0.54, p < 0.0001).ConclusionsIFN-score was increased in half of the iSLE patients, and given the correlation with complement and autoantibody diversity, this suggests a higher risk for disease progression. MxA in the blood and unaffected skin correlated strongly with the IFN-score and is possibly an easily applicable marker for IFN upregulation.
Incomplete systemic lupus (iSLE) is an acknowledged condition of patients with clinical signs of lupus who do not fulfill classification criteria for SLE. Some patients with iSLE have persistent mild disease, but others have serious organ involvement, and up to 55% progress to established SLE. Research on this subject could reveal predictive or diagnostic biomarkers for SLE. Ideally, it would become possible to discern those patients with critical organ involvement or a high risk for progression to SLE. This high‐risk group might benefit from early treatment, which would preferably be confirmed in randomized controlled trials. This process would, however, require agreement on a definition of iSLE. The Systemic Lupus International Collaborating Clinics (SLICC) classification criteria was composed in order to diagnose SLE earlier. The present review outlines the clinical characteristics of iSLE after introduction of SLICC criteria and furthermore proposes a definition of iSLE with the aim of discriminating the high‐risk group from those with a lower risk.
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