LICHEN PLANUS (LP) Lichen planus , the most typical and best characterized lichenoid dematosis, is an idiopathic inflammatory skin disease affecting the skin and mucosal membranes, often with a chronic course with relapses and periods of remission. CAUSES Drugs-including antimicrobials, antihypertensives, antimalarials, antidepressants, anticonvulsants, diuretics, metals, non‐ steroidal anti‐inflammatory drugs (NSAIDS) and more recently