When the pleura becomes diseased or otherwise produces a large amount of exudate in the chest cavity, the fibrin in the fluid accumulation attaches to the pleura or the granulation tissue proliferates, secondary to pleural fibrosis, which eventually leads to pleural thickening.
Common diseases are tuberculous pleurisy, abscess pleura, diffuse malignant pleural mesothelioma, pneumothorax, metastatic malignancy of the pleura, abdominal abscess, haemothorax and celiac disease.