Multiple solid and ground-glass density nodules may be caused by special pathogen infection in the lungs, interstitial fibrotic changes or lung cancer. 1. Special pathogen infection: special pathogen infection usually includes respiratory syncytial virus pneumonia and Staphylococcus aureus pneumonia, etc. Respiratory syncytial virus pneumonia can cause interstitial pneumonia and capillaritis in epidemic form, while Staphylococcus aureus pneumonia develops rapidly, and the patients usually have symptoms such as pallor and groaning. 2. Interstitial fibrosis: interstitial fibrosis is a kind of disease, the lungs are divided into lung parenchyma and interstitium, when interstitial fibrosis occurs, alveolar lesions will also occur, resulting in a large number of fibers deposition, thus causing oxygen can not enter the bloodstream, so that the body suffers from hypoxia, respiratory failure and other symptoms. 3. Lung cancer: Lung cancer is a common primary malignant tumor of the lungs, which may be caused by smoking and environmental exposure etc. It usually manifests as blood in sputum, chest pain and other symptoms, and in the late stage, there are hoarseness and shortness of breath etc. Patients are recommended to go to the hospital for checkup in time. Patients are advised to go to the hospital for timely examination and receive treatment under the guidance of the doctor.