A recent model-free linkage analysis of 21 sibling pairs with either BO or OAC also searched for new candidate genes, by definition representing rarer but high penetrance alleles, associated with ‘familial’ rather than ‘sporadic’ BO.41 This identified three: MSR1, ASCC1, and CTHRC1. Prospective evaluation reported an association with rs41341748 (MSR1) with a combination of BO/OAC, although no assessment was made for BO alone. This evidence concerns the gene MSR1 and bronchiolitis obliterans syndrome.