Lichen planus affects about 1%-2% of the general population. There is little known as to the cause of the condition, but all theories include a reaction of the body’s immune system. Lichen planus can develop nearly anywhere on the body. On the skin, lichen planus “appears as rows of itchy, flat -topped bumps,” It  can also appear on the inside of the cheek and on the gums and tongue. Lichen planus also appears on the scalp (referred to as lichen planopilaris). On the scalp, lichen planopilaris can cause permanent damage to hair follicles and leave adults with patches of baldness. Of those affected with the condition, about 10% will have lichen planus on the nails. The condition can cause splitting or thinning of the nails. One reason is it’s easy to confuse with other nail conditions, such as pterygium. Another roadblock to a diagnosis is the fact that lichen planus can show up on all the nails and toes, on only the nails or the toes, or on only select nails or toes. However, when lichen planus appears on the nail, it often destroys the matrix. Consequently, even if the lichen planus clears up, the nail will still be damaged. Lichen planus can be itchy, and it can cause inflammation. It may not be possible to clinically differentiate nail involvement by lichen planus from involvement by psoriasis, primary onychomycosis or traumatic nail unit dystrophy. One could reach a diagnosis of lichen planus on the basis of the typical clinical appearance and a punch biopsy of a representative lesion.