Our observation related to expression of circulating PIGR, a transmembrane glycoprotein important in immunoglobulin A transport across mucosal epithelial cells, is particularly intriguing, as prior work has demonstrated that the lungs of patients with IPF have ectopic expression of PIGR within areas of type 2 alveolar cell hyperplasia [22]. Here, PIGR is linked to idiopathic pulmonary fibrosis.