Lung 5mm high-density nodules may be caused by tuberculosis ball, lung inflammation and lung tumor. 1. Tuberculosis ball: If the respiratory tract and lungs are infected with Mycobacterium tuberculosis, the symptoms of tuberculosis ball may appear in the lungs, which may easily cause the phenomenon of high-density nodules in the lungs when CT radiography is taken. 2. Lung inflammation: if the lung is infected with bacteria, fungi and other pathogenic bacteria, it may cause inflammatory pseudotumor in the lung, which is not infectious and can be cured by timely treatment. 3. Lung tumors: when benign or malignant tumors appear in the lungs, high density nodules may also appear in the lungs, when necessary, pathological biopsy can be used to determine the benign or malignant nature of the tumor. Lung 5mm high-density nodules recommend early to the hospital to do the examination, clear cause and symptomatic treatment.