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
Acute activity-related toenail injuries are common among athletes and are typically caused by repetitive microtrauma, such as the nail plate striking footwear. Long-term complications include secondary fungal infections and nail plate deformities, including retronychia.
Nail-biting
Nail-biting (onychophagia) may not cause chronic problems. However, possible complications include the following:
Dystrophy
Infections (bacterial, viral, and/or fungal), typically resulting from small areas of nail trauma and damage
Dental problems
Dystrophy can develop if chronic nail-biting disrupts the nail unit, which often inflames the nail matrix. The nails can develop horizontal ridging, depressions, and raised areas. Nails can become shortened permanently because the distal nail bed becomes keratinized. The cuticles are almost always damaged, disrupting nails' waterproof "seal," causing nails to thin and peel, and increasing risk of infection. Eventually, scarring can affect the cuticles and matrix, making dystrophy irreversible.
Viral infections commonly include human papillomavirus, causing warts. Small areas of trauma all around the nail facilitate viral entry to the nails. These infections are difficult to eradicate and spread easily between fingers and from the fingers to the mouth and lips. Warts can be unsightly and distressing.
Bacterial infections are often due to staphylococcal and streptococcal species but may involve anaerobic bacteria, including Pseudomonas aeruginosa. Abscesses can develop that could lead to permanent nail loss without timely surgical drainage. Permanent dystrophy may develop even with surgical drainage.
Fungal infection, typically with Candida, is very common and can also occur among patients with chronically manicured nails. Usual features include swelling of the proximal and lateral nail folds and mild nail dystrophy, sometimes with distal onycholysis. Chronic trauma and/or manipulation of the cuticles and surrounding skin leads to chronic inflammation, facilitating microbial entry. Treatment with a topical antifungal, often combined with a topical corticosteroid, is usually effective if the patient stops nail-biting.
Dental complications may include teeth disfigurement or shifts in position. Risks of gingival disease and infection are also increased.
For many people, nail-biting is mild, and simply counseling them on the possible complications (which they often do not know) may encourage them to try to stop. Some are ashamed of nail-biting. Habit-breaking techniques may include applying over-the-counter nail polish that is foul-tasting or a long-wearing manicure that obstructs the person's ability to bite the nail, such as a dip-powder manicure. Rarely, severe or obsessive nail-biting can be a sign of a mental or anxiety disorder, necessitating referral to a mental health practitioner.
Onychogryphosis
Onychogryphosis is a nail dystrophy in which the nail, most often on the big toe, becomes thickened and curved. It may be caused by ill-fitting shoes. It is common among older people. Treatment consists of trimming the deformed nails.
Onychotillomania
In this disorder, patients pick at and self-mutilate their nails, which can lead to parallel transverse grooves and ridges (washboard deformity or habit-tic nail deformity). It most commonly manifests in patients who habitually push back the cuticle on one finger, causing dystrophy of the nail plate as it grows. Subungual hemorrhages can also develop in onychotillomania.
Subungual hematoma
Subungual hematoma occurs when blood becomes trapped between the nail plate and nail bed, usually as a result of trauma. Subungual hematoma may cause significant and throbbing pain, bluish black discoloration, and, unless small, eventual separation and temporary loss of the nail plate. When the cause is a crush injury, underlying fracture and nail bed or matrix damage may occur. Nail bed or matrix damage may result in permanent nail deformity.
If the injury is acute, nail trephination (eg, creating a hole in the nail plate using a cautery device, 18-gauge needle, or red-hot paperclip) can help relieve pain by draining accumulated blood; after 24 hours, blood is coagulated, thus trephination offers no benefit. It is not clear whether removing the nail and repairing any nail bed damage reduces risk of permanent nail deformity.
White spots
White spots on fingernails are generally of no concern. They usually occur as a result of a minor injury to the nail.
