Trachyonychia, or 20-nail dystrophy, is a benign nail disorder that primarily affects children. The condition may be idiopathic or associated with alopecia areata. Diagnosis of trachyonychia is based on the presence of nail roughness due to excessive longitudinal ridging or multiple small punctate depressions. One, a few, several, or all nails may be affected. The pathology shows that the disease is caused by inflammatory damage to the nail matrix due to spongiotic inflammation (72% of cases), psoriasis (10%), or lichen planus (16%). The prognosis of trachyonychia is benign, regardless of the disease which causes it. Treatment is unnecessary and often useless.