The MUC5B promoter polymorphism (rs35705950) is the most consistent genetic factor associated with IPF susceptibility, but data from Latin American populations remain limited.<h4>Methods</h4>We conducted a longitudinal cohort study including 50 patients with IPF and 45 healthy controls, recruited between August 1, 2018, and April 30, 2025, at a tertiary referral center in Brazil. Here, MUC5B is linked to idiopathic pulmonary fibrosis.