There are many reasons for changes in the shape and texture of the nails. Some changes, such as the minor pitting or the formation of ridges, occur with normal aging.
Other changes in the shape and texture of nails include the following:
Tube-shaped nails that curve inward (pincer nails) occur more often in toenails than fingernails and are caused by tight shoes. You may need to have the nail surgically removed or reconstructed if pain or infection is a problem. The nail may return to a normal shape if you begin to wear shoes that fit.
Spoon-shaped nails are more common in children and are usually temporary. They also occur with some diseases such as iron deficiency anemia. The nail will usually return to its normal appearance when the underlying disease is corrected.
Pitting. Minor pitting may be normal. Deep pitting, especially with yellow or thick nails or separation of the nail from the nail bed, can be caused by a skin disease, such as psoriasis or eczema.
Ridging may occur normally with aging but is also caused by injury, infection, or illness.
Thickened nails can be caused by a fungal infection, injury, or poor circulation. The nails may become thick, yellow, ridged, or brittle. The nail may loosen and fall off. A "ram's horn nail" is an unusually thickened nail that occurs with age.
Clubbing of the fingers is a condition in which ends of the fingers and toes swell and the nails bulge outward. The nails wrap around thickened fingers or toes, looking more raised, curved, and shiny than usual. This may occur normally but more often occurs in persons with chronic heart, lung, liver, or thyroid disease.