What is the difference between diffuse pleural thickening & focal pleural thickening? what is cause of each variant of pleural thickening?

Pleura: Focal pleural thickening may be residua of a prior bout of bacterial pneumonia. Diffuse pleural thickening is seen with more widespread pleural inflammation seen in autoimmune disease.like rheumatoid lung disease or pleural tuberculosis,but most often is due to asbestos exposure. A pulmonologist is best qualified to evaluate pleural thickening and recommend any further studies like ct scan or biop