Apical Mild Mild Apical Pleural Thickening X-ray Pleural Thickening X-ray Mild Apical Pleural Thickening X-ray leslieericadism Friday, March 9, 2018 Causes of pleural thickening pleural thickening. Pleural thickening is a condition of the lungs that is most often caused by the long term e...