OBJECTIVE: To study the association between polymorphisms in the mannose-binding lectin gene (MBL2) and disease activity, physical disability, and joint erosions in patients with newly diagnosed rheumatoid arthritis (RA). METHODS: Patients with early RA (n=158) not previously treated with disease modifying antirheumatic drugs, participating in a treatment trial (CIMESTRA study) were examined at inclusion for MBL2 pooled structural genotypes (O/O, A/O, A/A), regulatory MBL2 promoter polymorphism in position -221 (XX, XY, YY), anti-cyclic citrullinated peptide 2 antibodies (anti-CCP2), disease activity by Disease Activity Score-28 (DAS28 score), physical disability by Health Assessment Questionnaire (HAQ) score, and erosive changes in hands and feet (Sharp-van der Heijde score). RESULTS: Eight patients were homozygous MBL2 defective (O/O), 101 belonged to an intermediate group, and 49 were MBL2 high producers (YA/YA). Anti-CCP was present in 93 patients (59%). High scores of disease activity, C-reactive protein-based DAS28 (p=0.02), and physical disability by HAQ (p=0.01) were associated with high MBL2 expression genotypes in a gene-dose dependent way, but only in anti-CCP-positive patients. At this early stage of the disease there was no association with erosion score from radiographs. CONCLUSION: The results point to a synovitis-enhancing effect of MBL in anti-CCP-positive RA, whereas such an effect was not demonstrated for joint erosions.