Of the 12 cytokines analyzed, IL‐4, IL‐2, TNF‐α, and IL‐17A, all involved in the fibrotic process, were more highly expressed in patients with PCLF than in those with IPF (p < 0.001), whereas IP‐10 and MCP‐1 were expressed to a lesser degree (p < 0.001). Here, IL4 is linked to idiopathic pulmonary fibrosis.