To elucidate the genetic susceptibility to an environmental insult that results in ASyS, López-Mejías et al. looked to a polymorphism of the MUC5B gene (rs35705950), which is associated with idiopathic pulmonary fibrosis (IPF), chronic hypersensitivity pneumonitis (CHP), and RA-ILD. The gene discussed is MUC5B; the disease is rheumatoid arthritis.