Smoking is a major risk factor for IPF, and studies have shown that patients with smoking-related lung diseases such as pulmonary Langerhans cell histiocytosis (PLCH) and desquamative interstitial pneumonitis (DIP) have much higher levels of SPP1 expression in BAL cells compared to those from IPF subjects [29]. The gene discussed is SPP1; the disease is idiopathic interstitial pneumonia.