Articles Mannose-binding lectin defi ciency and disease severity in non-cystic fi brosis bronchiectasis: a prospective study

Background Mannose-binding lectin (MBL) is a key component of innate immunity. MBL defi ciency is common (10–30 % of the general population depending on the defi nition used) and has been associated with disease progression in cystic fi brosis. We aimed to assess the eff ect of MBL defi ciency on disease severity in non-cystic fi brosis bronchiectasis. Methods We recruited patients with non-cystic fi brosis bronchiectasis and age-matched and sex-matched controls at a specialist bronchiectasis clinic in Edinburgh, UK. We assessed MBL function with genotyping (low-expressing genotype [defi ciency] defi ned as homozygosity for exon 1 mutations [YO/YO] or compound heterozygosity [XA/YO]; YA/YO and XA/XA genotypes were defi ned as intermediate-expressing with all other genotypes defi ned as high-expressing) and serum measurements (defi ciency defi ned with two parameters: <500 ng/mL or <200 ng/mL). We assessed rates of exacerbation, chronic bacterial colonisation, and lung function during 4 years of follow-up. Findings We included 470 patients with bronchiectasis and 414 controls. MBL genotype frequencies and MBL serum concentrations did not diff er between patients and controls. 55 (12%) patients with bronchiectasis had low-expressing genotypes. These patients had a mean of 2·7 exacerbations per year (SD 1·8), compared with 1·9 per year (1·2) for 135 patients with intermediate-expressing genotypes and 1·9 per year (1·3) for 280 patients with high-expressing genotypes (p<0·0001). Chronic colonisation with bacteria was most frequent in patients wit