Alpha-1-antitrypsin deficiency [AATD] is associated with variable development of emphysema and other features of chronic obstructive pulmonary disease [COPD]. Matrix metalloproteinases [MMPs] are believed to be important in the pathophysiology of COPD, and may therefore confer susceptibility to this phenotype in patients with AATD. OBJECTIVES: to assess the role of polymorphism of MMP1, MMP3 and MMP12 in AATD phenotypes. METHODS: 424 PiZZ subjects from the UK AATD Registry were assessed for history of chronic bronchitis [CB], post-bronchodilator lung function impairment and decline of lung function. Tag single nucleotide polymorphisms (SNPs) for MMP1, MMP3 and MMP12 were chosen using HapMap [r(2)>0.8, MAF>0.05] and were genotyped using TaqMan genotyping technologies. Quantitative genetic association was assessed using regression modelling to correct for covariates. RESULTS: in patients with AATD, carriers of the G allele of rs678815 [MMP3] had lower gas transfer [KCO] [P = 0.025, B =-7.766] than the homozygous wild type, while carriers of the T allele of rs470358 [MMP1] had higher KCO [P = 0.025, B = 6.130]. CONCLUSIONS: variations in MMP1 and MMP3 are associated with gas transfer in AATD, supporting a previous family study showing linkage of KCO to this gene region. Replication of these preliminary data is now required particularly if MMP inhibitors are to be considered as a therapeutic option.