Previous studies, based on patients enrolled in the UK PIN registry, found individuals with PAD who had reduced concentrations of both IgA (<0.8 g/L) and IgM (<0.5 g/L) were more significantly more likely to have a diagnosis of bronchiectasis, compared to those with normal serum concentrations of these immunoglobulin isotypes [10]. This evidence concerns the gene CD40LG and bronchiectasis.