The nail unit is made up of the nail plate and the surrounding structures. These structures include the nail bed, which underlies the nail and forms the attachment of the nail to the finger; the nail matrix, which is located at the base of the nail and is the site of nail growth; the cuticle, which connects the top of the nail plate to the skin behind it; and the nail folds (the folds of hard skin) at the sides of the nail plate, which is where the skin and nail meet.

Did You Know... Some babies are born without nails, a condition called anonychia.

Causes

Many disorders can affect the nails. These disorders can affect any portion of the nail unit and can impact the appearance of the nail plate itself. Nail disorders can result from:

• Infections
• Injuries
• Internal diseases (such as certain lung diseases, which can cause yellow nail syndrome)
• Structural problems (such as an ingrown toenail)

Spotlight on Aging
With aging, nails become dry and brittle and flat or concave instead of convex. They may develop ridges along their length. Nail color may change to yellow or gray. Brittle nails may split. Toenails require special attention in older people and in people with diabetes or peripheral vascular disease. Such people may have poor sensation in their feet, which increases the risk of injury when they try to trim their nails. A foot doctor (podiatrist) can help care for their nails to prevent local breakdown and secondary infections.

Last full review/revision August 2007 by Wingfield E. Rehmus, MD, MPH