Left rib pain signals pneumonia, pleural disease, coronary heart disease and other diseases. 1. Pneumonia: When inflammation occurs in the lower part of the left lung, it can involve the pleura and cause chest pain symptoms. Especially when coughing, deep inhalation and rotating position, it leads to aggravation of chest pain, which can be alleviated or disappeared when breath is held. 2. Pleural disease: for example, when pleural inflammation or tumor occurs, it can lead to hidden pain below the left rib cage. At this time, it is recommended to go to the hospital as soon as possible, and can be diagnosed by chest X-ray or chest CT for treatment. 3. Coronary heart disease: common in angina pectoris or acute myocardial infarction. Paroxysmal chest pain may occur at the ribs of the left chest. In angina pectoris, the pain usually lasts for a few minutes, and the symptoms can be relieved on their own, or after taking nitroglycerin. 4. Others: diseases such as costal neuritis, herpes zoster, rib fracture or soft tissue injury can also cause left rib pain. It is recommended to go to the hospital in time, in order to clarify the cause of the disease, so as to facilitate the symptomatic treatment, which is conducive to a speedy recovery.