Merck Manual

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Overview of Nail Disorders

By

Chris G. Adigun

, MD, Dermatology & Laser Center of Chapel Hill

Reviewed/Revised Dec 2021 | Modified Sep 2022
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Topic Resources

The nail unit is made up of the nail plate (the hard part of the nail made of the protein keratin) and the surrounding structures. The nail bed is underneath the nail and attaches the nail to the finger. The nail matrix is located at the base of the nail and is where nail growth originates. The cuticle connects the top of the nail plate to the skin behind it. The lunula is the half-moon shape at the base of the nail. The nail folds are the folds of hard skin at the base and sides of the nail plate where the nail and the skin meet.

Did You Know...

  • Some babies are born without nails, a condition called anonychia.

Causes of Nail Disorders

Some of the causes of nail disorders include the following:

Spotlight on Aging: Nail Disorders

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 ( see Foot problems in diabetes Foot problems in diabetes People with diabetes mellitus have many serious long-term complications that affect many areas of the body, particularly the blood vessels, nerves, eyes, and kidneys. (See also Diabetes Mellitus... read more Foot problems in diabetes ) or peripheral vascular disease ( see Foot care Foot care Occlusive peripheral arterial disease is blockage or narrowing of an artery in the legs (or rarely the arms), usually due to atherosclerosis and resulting in decreased blood flow. Symptoms depend... read more Foot care ). 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 skin breakdown that can lead to infections.

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