The consequences of lung inflammation depend on the cause of the inflammation. Lung inflammation can refer to irritation and infection of the lung itself, or of the thin membrane that covers the lungs and lines the chest cavity, known as the pleura. When the pleural sacs become inflamed, it is known as pleurisy, and it can result in fluid accumulating between the two pleural layers, known as a pleural effusion.

In pneumonia, the lung tissue itself becomes infected, usually due to bacteria. It is one of the main reasons for lung inflammation, and causes a phlegm-filled cough, chest pain when you breathe, shortness of breath, and fever. Tuberculosis is another, highly contagious bacterial infection that can cause lung inflammation. It can cause a chronic, phlegmy cough, night sweats and fevers. Pneumonia and tuberculosis can both cause pleurisy, which may cause sharp chest pain when inhaling, coughing or sneezing. Pleurisy can also be caused by lupus, rheumatoid arthritis, cancer, a pulmonary embolism, liver diseases, or a drug reaction.

In severe cases, lung inflammation can lead to the formation of a lung abscess, a pus-filled cavity surrounded by inflammation, or an empyema, a collection of pus in the pleural space. Both these complications are very serious conditions that need antibiotic treatment, and maybe even surgery to remove the abscess or drain the pus. Another extreme consequence of pneumonia is acute respiratory distress syndrome, which can be fatal. The lung's air sacs fill with fluid, and the respiratory failure ensures. This complication has a high fatality rate and requires a patient to be in an intensive care unit, receiving aggressive treatment including receiving extra oxygen with the help of a ventilator and antibiotics.