If you have itchy, angular, purple bumps on your skin, particularly on your forearms or have white patches in your mouth, check with a dermatologist, you may have lichen planus.

The only way to prove a diagnosis of lichen planus is to have your skin biopsy show its characteristic appearance. Doctors don't have the foggiest idea of the cause, although reaction to drugs and infection are possible. Lichen planus has been associated with at least 30 drugs, and has been reported in people who work with color film developers and those afflicted with a muscle disease called polymyositis; malabsorption syndromes in which people cannot absorb certain nutrients in foods; or a type of cancer called lymphoma.

Since doctors do not know the cause, they are unable to offer a cure. The only effective treatments for the bitter itching are cortisone-type drugs. Because cortisones can have serious side effects, doctors reserve pills and high dose injections for occasional use, but creams and tapes applied to individual lesions help a little bit, while injections of cortisones into mouth and skin lesions are highly effective. There is no effective treatment for deformed nails. Sometimes lichen planus goes away by itself in one or two years or even after 15 years.