A variety of disorders can affect nails, including deformities Nail Deformities and Dystrophies Deformities are often considered together with dystrophies, but the two are slightly different; deformities are generally considered to be gross changes in nail shape, whereas dystrophies are... read more 
, trauma Nail Trauma Fingernails and toenails can be damaged by injuries. Diagnosis is clinical. Treatment varies by cause. Nail trauma is common. Resulting disorders can include Activity-related toenail injury... read more 
, infections of the nail Onychomycosis Onychomycosis is fungal infection of the nail plate, nail bed, or both. The nails typically are deformed and discolored white or yellow. Diagnosis is by appearance, wet mount, culture, polymerase... read more 
, paronychia Acute Paronychia Paronychia is infection of the periungual tissues. Acute paronychia causes redness, warmth, and pain along the nail margin. Diagnosis is by inspection. Treatment is with antistaphylococcal antibiotics... read more 
, retronychia Retronychia Retronychia is a less common form of paronychia, which is infection of the periungual tissues. Acute symptoms include pain, inflammation of the proximal nail fold, xanthonychia, onycholysis... read more 
, and ingrown toenails Ingrown Toenail An ingrown toenail is incurvation or impingement of a nail border into its adjacent nail fold, causing pain. (See also Overview of Nail Disorders.) Causes of ingrown toenail include tight shoes... read more 
. Nail changes may occur in many systemic conditions and genetic syndromes or result from trauma.
Most nail infections are fungal (onychomycosis Onychomycosis Onychomycosis is fungal infection of the nail plate, nail bed, or both. The nails typically are deformed and discolored white or yellow. Diagnosis is by appearance, wet mount, culture, polymerase... read more ), but bacterial and viral infections can occur (eg, green-nail syndrome Discoloration [Pseudomonas], herpetic whitlow Herpetic Whitlow Herpetic whitlow is a cutaneous infection of the distal aspect of the finger caused by herpes simplex virus. (See also Overview and Evaluation of Hand Disorders.) Herpetic whitlow may cause... read more 
[herpes simplex virus-1]). Even parasitic infestation such as crusted scabies Scabies Scabies is an infestation of the skin with the mite Sarcoptes scabiei. Scabies causes intensely pruritic lesions with erythematous papules and burrows in web spaces, wrists, waistline... read more 
can lead to changes in the nail plate. Paronychia is not actually an infection of the nail but rather of periungual tissues.
Common warts Warts Warts are common, benign, epidermal lesions caused by human papillomavirus infection. They can appear anywhere on the body in a variety of morphologies. Diagnosis is by examination. Warts are... read more 
(verrucae vulgaris) result from human papillomavirus infection and frequently infect the proximal nail fold and sometimes the subungual area. Onychophagia (nail-biting) can help spread this infection. Warts involving these areas are especially difficult to treat.
Toenails require special attention in older people and in people with diabetes or peripheral vascular disease; a podiatrist can help avoid local breakdown and secondary infections by assisting in routine nail trimming.
