Characterization of a subset of patients with primary Sjögren's syndrome initially presenting with C3 or C4 hypocomplementemia.

In this population of patients with pSS, low C3 and C4 levels at diagnosis were associated with extraglandular manifestations such as vasculitis and interstitial lung disease, as well as disease activity and damage accrual. These results suggest that complements C3 and C4 have clinical and prognostic value in patients with pSS.