A 14-year-old boy presents with a history of multiple ingrown nails of both great toes. Today his right big toe is swollen and painful (Figure 192-1). He has a 2-week history of pain, redness, and swelling of the lateral nail fold of the right great toe. Soaking the toe in Epsom salts has not helped. A partial nail removal after a digital block was successful. The nail matrix was also ablated with phenol to prevent recurrence of the ingrown nail.

Onychocryptosis (ingrown toenails) is a common childhood and adult problem. Patients often seek treatment because of the significant levels of discomfort and disability associated with the condition.

Onychocryptosis, unguis incarnatus.

The prevalence of onychocryptosis is unknown as many patients do not seek medical care and it is not a reportable disease. The toenails, especially the great toenail, are most commonly affected. Ingrown toenails at birth and in early childhood do occur, but are very rare.

Onychocryptosis occurs when the lateral nail plate damages the lateral nail fold. The lateral edge of the nail plate penetrates and perforates the adjacent nailfold skin. Perforation of the lateral fold skin results in painful inflammation that manifests clinically as mild edema, erythema, and pain. In advanced stages, drainage, infection, and ulceration may be present. Hypertrophy of the lateral nail wall occurs, and granulation tissue forms over the nail plate and the nailfold during healing of the ulcerated skin.1 It is a common affliction that can result from a variety of conditions that cause improper fit of the nail plate in the lateral nail groove (Figure 192-1).

See reference 1.

• Genetic predisposition.
  
• Poor-fitting footwear.
  
• Excessive trimming of the lateral nail plate.
  
• Pincer nail deformity (Figure 192-2).
  
• Trauma.
  
• Sports in which kicking or running is important.
  
• Hyperhidrosis.
  
• Anatomic features such as nailfold width.
  
• Congenital malalignment of the digit.
  
• Overcurvature of the nail plate.
  
• Onychomycosis and other diseases that result in abnormal changes in the nail plate.

Clinical Features: History and Physical

The diagnosis is based upon clinical appearance and rarely is difficult. Characteristic signs and symptoms include pain, edema, exudate, and granulation tissue (Figure 192-1).

Typical Distribution

The great toe is most commonly affected; fingers are rarely involved except when nail biting is present.

• Cellulitis—Presents with redness, pain, and swelling beyond the nail fold (see Chapter 120, Cellulitis).
  
• Paronychia—Presents with redness and abscess formation (pus) in a nail fold (see Chapter 194, Paronychia).