Many disorders can affect the nails, including deformity and dystrophy, infections, and ingrown toenails. Infections can involve any part of the nail and may or may not change the nail’s appearance. Most nail infections are fungal (onychomycosis), but bacterial and viral infections occur in Nail Problems.

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 sides of the nail plate where the nail and the skin meet.

Causes of Nail Disorders

Some of the causes of nail disorders include the following:

  • Infections (such as paronychia, warts, and green nail syndrome)
  • Injuries
  • Internal diseases (such as certain lung diseases, which can cause yellow nail syndrome)
  • Nail fungus (onychomycosis)
  • Structural problems (such as an ingrown toenail)
  • Birth deformities (such as pachyonychia congenita)
  • Drugs
  • Tumors

Deformities, Dystrophies, and Discoloration of the Nails

The terms deformities and dystrophies are often used interchangeably, sometimes even by doctors. However, their meanings are slightly different.

  • Deformities: Changes in nail shape
  • Dystrophies: Changes in nail texture, color, or both

Doctors more commonly use the term dystrophy than deformity.

About 50% of nail dystrophies are caused by a fungal infection (onychomycosis) . The remainder result from various causes, including nail injuries, birth deformities of the nails, psoriasis, lichen planus, and occasionally tumors (cancerous and noncancerous). Drugs, infections, and diseases can cause discoloration of the nails (chromonychia). For example, infection with Pseudomonas bacteria can cause a greenish discoloration.

The doctor can often make the diagnosis of nail dystrophies caused by a fungus by examining the nails. However, to confirm the diagnosis, the doctor may need to take fungal scrapings and do a culture (the process of growing the organisms in a laboratory) or do a polymerase chain reaction (PCR) analysis to look for genetic material from a fungus.

To diagnose nail dystrophies that are not caused by a fungus, doctors may do a biopsy of the nail plate (the hard part of the nail) or nail matrix (located at the base of the nail and where nail growth originates).

If the nail’s appearance does not improve with treatment of the underlying disorder, manicurists may be able to hide deformities and some dystrophies with appropriate trimming and polishes.

Birth deformities of the nail

Some babies are born without nails (anonychia). In nail-patella syndrome, thumbnails are missing or are small with pitting and ridges. Darier disease causes red and white streaks on the nails and V-shaped notches to form on the tips of the nails. In pachyonychia congenita, nail beds (the parts of the nail unit that attach the nail to the finger) are thickened and discolored and are curved from side to side, forming a pincer nail deformity.

Nail deformities and dystrophies associated with systemic diseases
Sometimes, diseases that involve other organs (systemic diseases) can cause changes in the nails as well, including the following:


  1. Iron deficiency may cause spoon-shaped nails (koilonychia). This deformity is particularly characteristic of Plummer-Vinson syndrome.
  2. Kidney failure may cause the bottom half of the nails to turn white and the top half of the nails to turn pink or appear pigmented (half-and-half nails or Lindsay nails). This dystrophy can also occur in healthy people.
  3. Cirrhosis may cause the nails to turn white, although the very top part of the nails may remain pinker. Intensely white nails, also called Terry nails, can be present not only in people with cirrhosis but also in those with chronic heart failure or diabetes. Terry nails may sometimes occur as part of normal aging. Low blood levels of the protein albumin (which may occur in people with cirrhosis) can cause horizontal white lines to form on the nails.
  4. Some lung diseases, often accompanied by lymphedema (an accumulation of lymphatic fluid in tissues), may cause yellow nail syndrome, in which nails become thick, overcurved, and yellow or yellow-green in color.
  5. Beau lines are horizontal grooves in the nail that occur when there is temporary slowing of growth of the nail. Sometimes the grooves can go all the way through the nail, leading to complete loss of the nail. They can occur after an infection, injury, systemic illness, or chemotherapy.
  6. White horizontal lines across part of the nail (leukonychia) may appear after an injury. However, lines that run horizontally all of the way across the nail (Mees lines) may be associated with more serious health problems, including cancer or heart failure, chemotherapy, or exposure to certain toxins, such as arsenic, thallium, or other heavy metals. The nails can grow out normally if exposure to these toxins or chemotherapy is stopped.