Chlamydia pneumoniae and age-related macular degeneration: a role in pathogenesis or merely a chance association?

The role of inflammation in the aetiology of age-related macular degeneration (AMD) has become very topical as the discovery that genetic variation in complement pathway genes influences the risk of developing AMD. Complement factor H gene, an inhibitor of the alternative complement activation pathway along with other complement pathway genes factor F (BF) and C2 show significant contribution to the risk of AMD. The alternative complement pathway is activated by a trigger, which is often microbial in nature. One current model of AMD aetiology implicates aberrant regulation of the alternative pathway of complement, in combination with some unknown infectious agents. Chlamydia pneumoniae could be one such potential trigger of the alternative complement pathway and several investigations have linked C. pneumoniae to AMD. However, there are only a few studies to date and numbers in most studies are small. Also there are many difficulties in verifying laboratory techniques for the detection of C. pneumoniae chronic infection. As such we need to be cautious not to over interpret the current results. However, the findings certainly give impetus for further work on C. pneumoniae and AMD. This paper provides an overview of work in this area.