Objectives To evaluate the presence of lymphocyte aggregates in synovial tissue of patients with early arthritis in relationship to clinical outcome and to determine whether this is a stable feature over time.

Methods Arthroscopic synovial biopsy samples were collected in a prospective cohort of disease-modifying antirheumatic drug-naïve patients with early arthritis (<1 year's disease duration) at baseline (n=93) and, if rheumatoid arthritis was suspected, after 6 months of follow-up (n=17). After 2 years of follow-up, definitive diagnosis and clinical outcome were assessed. Size of synovial lymphocyte aggregates was graded (score 1–3). Lymphoid neogenesis (LN) was defined by the presence of grade ≥2 aggregates and subclassified based on the presence of follicular dendritic cells (FDCs).

Results LN was present in 36% of all patients and FDCs in 15% of patients with LN. Presence of lymphocyte aggregates differed over time. LN was associated with the degree of synovial inflammation. There was no relationship between the presence of lymphocyte aggregates at baseline and definitive diagnosis or clinical outcome after follow-up.

Conclusions Presence of lymphocyte aggregates is a dynamic phenomenon related to the degree of synovitis and can be detected in different forms of early arthritis. This feature does not appear to be related to clinical outcome.