idiopathic
adjective medical specialized uk/ˌɪd.i.əˈpæθ.ɪk/ us/ˌɪd.i.əˈpæθ.ɪk/
特发的，自发的，原因不明的（疾病）
an idiopathic disease or medical condition has no known cause
Idiopathic pulmonary fibrosis is a lung condition which causes scarring of the lungs. 特发性肺纤维化是一种造成肺部形成瘢疤的疾病。