CHI3L1 and cryptogenic organizing pneumonia: YKL-40 levels have been shown to associate also with other idiopathic interstitial lung diseases including nonspecific interstitial pneumonia, smoking-related interstitial lung disease, and cryptogenic organizing pneumonia [16], pulmonary sarcoidosis [22], posttransplantation bronchiolitis obliterans [23], and pulmonary manifestations of cystic fibrosis or systemic sclerosis [24–26].