The observation that low frequency stimulation of the postero-basal lung base, where fibrosis is often most extensive, induces cough in more patients than at other sites is consistent with the hypothesis that lung distortion is a contributory factor to the pathogenesis of cough in IPF, possibly by activating RARs or destruction of inhibitory c-fibres. This evidence concerns the gene RARS1 and idiopathic pulmonary fibrosis.