When HP patients were sub-grouped based on their high-resolution computed tomography (HRCT) patterns, the fHP group exhibited markedly higher plasma levels of GDF15 compared to the non-fHP group (2539 ± 821 pg/ml versus 1783 ± 801 pg/ml (p = 0.009) (Fig. 2). This evidence concerns the gene GDF15 and hypersensitivity pneumonitis.