[Key messages in nail disease].

Nail diseases are varied, and their diagnosis is often difficult. Misdiagnosis can result in failure to recognize a severe disease in urgent need of treatment and in the prescription of treatments that are inappropriate, long, ineffective, and expensive. Acute paronychia must be managed rapidly, treated with antiseptics several times a day, and closely monitored. Nail lichen must be recognized early and treated rapidly and appropriately to prevent permanent scarring. All chronic pain (to shocks or cold) of the tip of a finger or toe should suggest a glomus tumor. Any unexplained persistent single-finger onychopathy should in principle cause the physician to suspect a tumor, carcinoma, or melanoma and to order a histologic examination. An onychopathy must not be treated as an onychomycosis without diagnostic certainty. Repeated microtraumas of the toenails cause injuries that absolutely must be differentiated from onychomycosis. In growth of the big toenail can often be avoided by appropriate cutting of the nails, leaving in place the lateral parts of the nail plate.