The thickness ranges from less than 1 mm up to 1 cm or more and may extend for a few millimeters into the lung parenchyma.[2] Fibrous strands (“crow's feet”) extending from the thickened pleura into the lung parenchyma can be often detected on CT scan. Diffuse pleural thickening develops 20 to 40 years after first exposure.[11] All types of asbestos can cause diffuse pleural thickening and a dose-related relationship has been described.[4] It is thought that asbestos fibres that reach the pleura induce subpleural fibroblasts and mesothelial cells to produce scar tissue and collagen deposition, resulting in subpleural thickening.[6] Pleural plaques often coexist with DPT although the latter is rare compared with pleural plaques. According to the Australian Surveillance of Australian Workplace Based Respiratory Events (SABRE) scheme, DPT accounted for 22% of all asbestos-related diseases.[12] It usually begins with an inflammation of the pleura that is accompanied by a pleural effusion.