Clinical characteristics and prognosis of primary Sjögren's disease patients with hypocomplementemia: reduced C3 is independently associated with new-onset peripheral cytopenias.

Hypocomplementemia in SjD is associated with higher disease activity, immune dysregulation, and a greater prevalence of peripheral cytopenias.

Decreased C3, but not C4, is independently associated with new-onset peripheral cytopenias, supporting further investigation of C3 as a candidate biomarker for risk stratification.

Key Points • Hypocomplementemia is common in primary Sjögren's disease and is associated with younger age at onset, female predominance, and higher disease activity.