Leukotriene (LT) B4, a metabolite synthesized by 5-lipoxygenase (5-LO), was elevated in bronchoalveolar (BAL) fluid of patients with IPF [4] and deletion of 5-LO leading to a deficiency in sulphidopeptide-leukotriene production ameliorated bleomycin-induced fibrosis in mice [5]. The gene discussed is ALOX5; the disease is idiopathic pulmonary fibrosis.