SFTPD and pulmonary fibrosis: The subclassifications of IP were idiopathic pulmonary fibrosis (IPF) in 1 patient, IIP other than IPF in 3 patients, pneumoconiosis in 1 patient and asbestos-related disease in 1 patient (serum lactate dehydrogenase, 241 IU/l (range, 166–227 IU/l); serum surfactant protein D, 97.4 ng/ml (range, 72–237 ng/ml); serum sialylated carbohydrate antigen, 509 U/ml (range, 362–1506 U/ml)).