Patients with elevated-GMAb HP presented with older age (p = 0.039), higher lymphocyte counts in BAL (p = 0.019), and higher serum levels of KL-6 (p = 0.001), SP-D (p = 0.004), carcinoembryonic antigen (CEA) (p = 0.023), and cytokeratin fragment 21-1 (CYFRA) (p = 0.001) than did patients with low-GMAb HP. This evidence concerns the gene CEACAM5 and hypersensitivity pneumonitis.