Fibrous streaks in the lower lobe of the left lung are generally not serious, and are usually a manifestation of repaired disease or repaired lung injury, mostly old scarring left after the healing of pneumonia, tuberculosis, and so on. Fibrous striae in the lower lobe of the left lung refers to a dense shadow with striae-like manifestations in the lower lobe of the left lung found on chest imaging. This striae shadow does not specifically refer to a disease, but is simply a manifestation of the disease or lesion in the lung images. After pneumonia or tuberculosis, because the lungs repair themselves after injury, i.e., fibroblasts proliferate to form fibrotic-like foci, which in turn form striated shadows. Streak shadows are a manifestation of the mechanization of lung tissue and are left behind by the repair of the disease, and usually do not require treatment. However, if there are multiple fibrous streaks, accompanied by cough, sputum, chest pain and other symptoms, it should be taken seriously, and further examination is needed to clarify whether there are other diseases, such as secondary bronchiectasis. When fibrous streaks are found in the lower lobe of the left lung, patients are advised to go to the hospital as soon as possible to avoid delaying their condition.