AbstractAim: To investigate the correlation of six functional polymorphisms in the MBL gene with MBL plasma levels in relation to periodontitis.Material and Methods: A total of 92 periodontitis patients and 70 controls, all of Caucasian origin, were included. Patients and controls were genotyped for the L/H, X/Y, P/Q, A/D, A/B and A/C polymorphisms. Distributions of genotypes, rate of allele carriage and allele frequencies were compared between patients and controls. Patients and controls were subdivided in groups of genotypes. Plasma MBL levels were compared between different genotype groups.Results: On the basis of genotyping, three phenotypes with regard to mannose‐binding lectin (MBL) production were distinguished: high‐producers, low‐producers and deficient subjects. No differences in the genotype frequencies were observed between patients and controls. Within patients and controls, subjects with the high‐producing genotypes had significantly higher MBL plasma levels than low‐producers and deficient subjects (p<0.001). Plasma MBL was higher in low‐producer patients compared with low‐producer controls (padjusted=0.021).Conclusion: No association could be observed between MBL gene polymorphisms and susceptibility to periodontitis in Caucasians. However, now that genotyping could distinguish the low producing and deficient subjects from the high‐producers, it was observed, for the first time, that MBL acts as a weak acute‐phase protein in periodontitis.