Background Mannose binding lectin MBL deficiency, encoded by variant MBL2 genotypes, seems to influence severity and outcome of lung disease in cystic fibrosis CF patients. Literature data are uncertain regarding the role of MBL deficit as a predictor factor for poor outcome in CF.

Objectives The assessment of serum MBL levels among CF children with severe lung disease and evaluation of MBL deficiency as risk factor.

Methods Group 1 included 15 children with classic CF, F508 homozygotes, age between 618 years, with severe lung disease. Group of controls included 14 healthy children. Patients were age and gender matched. Children associating diseases who influence MBL level were excluded. Clinical data, lung function parameters and microbiology results were obtained from our National CF Centres database. MBL was dosed using MBL ELISA Oligomer kit. Data were statistically analyzed with ANOVA and Students t test.

Results Among group 1 children with CF serum MBL levels average was 3042.747ngml, with 30 lower comparing to controls. Deficit of MBL serum levels was recorded in 57 CF children others had normal or increased MBL levels.

Conclusions Lower MBL average in CF patients sustains MBL deficiency as associated factor for severe CF lung disease. Possible explanation of increased MBL level in CF patients could be increased growth hormone levels in childhood or predominance of wild MBL2 genotype in our patients. Longitudinal evaluation of MBL levels and MBL2 genotyping would be useful to identify the patients predisposed to worse lung disease outcome.