How do you get lichen planus? I had it since 2003 every doctor I've gone to doesn't know I got it. No one in my family has it.

Autoimmunity. Lichen planus is an immune system reaction often associated with autoimmune diseases like ulcerative colitis, vitiligo or dermatomyositis. It can also be associated with hepatitis, so you should have a workup for chronic hepatitis especially if you do not have any other autoimmune disease.
Lichen planus. Nobody knows what the exact causes of lichen planus are. We know it can be triggered by taking certain medications, including thiazide diuretics, antimalarials and phenothiazines (a group of tranquilizing drugs with antipsychotic actions). A significant number of skin specialist doctors (dermatologists) believe it might be classified as an autoimmune disease. A higher-than-normal percentage, hepc+.