A variety of disorders can affect nails, including deformities, infections of the nail, paronychia, and ingrown toenails (see Nail Disorders: Ingrown Toenail). Nail changes may occur in many systemic conditions and genetic syndromes.
Nails may also undergo changes due to local infection or trauma. For example, trauma to the finger may cause changes in the nail. The nail may develop a white coloration that starts at the nail bed and grows up with the nail. Sometimes, if a nail becomes separated from the nail bed, a new nail grows below the existing nail and replaces it when fully grown in.
Most nail infections are fungal (onychomycosis—see Nail Disorders: Onychomycosis), but bacterial and viral infections can occur (eg, green-nail syndrome [Pseudomonas], herpetic whitlow [herpes simplex virus-1]). Paronychia is not actually an infection of the nail but rather of periungual tissues.
Common warts (verrucae vulgaris) result from papillomavirus infection and frequently infect the proximal nail fold and sometimes the subungual area. Onychophagia (nail-biting) can help to spread this infection. Warts involving these areas are especially difficult to treat. Freezing with liquid nitrogen may be effective.
Toenails require special attention in the elderly and in people with diabetes or peripheral vascular disease; a podiatrist can help avoid local breakdown and secondary infections.
Last full review/revision October 2009 by Wingfield E. Rehmus, MD, MPH