What happens if pleurisy is not treated is analyzed and judged on a case-by-case basis. In the case of mild pleurisy, such as that produced by general inflammation, most can be cured by autoimmunity, so it will not affect the body greatly. If it is due to a more specific bacterial infection, such as pleurisy infected by tuberculosis bacteria, it can lead to the production of pleural effusion. Especially if left untreated, it can lead to an increasing amount of pleural fluid, which can eventually compress the lung tissue, thus causing chest tightness, shortness of breath, and difficulty breathing. If left untreated, it may form encapsulated pleural effusion and even cause thoracic deformity and respiratory failure. Therefore, regardless of the type of pleurisy, it is necessary to go to the hospital in time to identify the specific cause and take targeted treatment.