Description

• In an ingrown toenail, the distal margin of the nail plate grows into the lateral nail fold, causing irritation, inflammation, and sometimes bacterial or fungal infection:
  • Stage 1 (inflammation): erythema, edema, tenderness to palpation of lateral nail fold
  • Stage 2 (abscess): increased pain, erythema, and edema as well as drainage (purulent or serous)
  • Stage 3 (granulation): Chronic inflammation leads to further erythema, edema, and pain, often with granulation tissue growing over the nail plate and significant nail fold hypertrophy.
• Can reoccur
• Synonym(s): onychocryptosis, unguis incarnatus

Epidemiology

• Great toenail is most often affected.
• Lateral edge of nail is more commonly affected than the medial edge.
• Most common in males aged 14 to 25 years
• Infrequent, but more often in elderly females than in elderly males
• More common in those with lower incomes

Prevalence

• 2.5% of total population
• 5% of population aged > 65 years
• 2:1 male to female ratio

Etiology and Pathophysiology

• Nail plate penetrates the nail fold, causing a foreign body reaction (inflammation).
• Bacteria or fungi may enter through the opening in the nail fold, causing infection and abscess formation.
• The inflamed and infected area leads to granulation tissue and hypertrophy of the nail fold.

Risk Factors

• Genetic factors
  • Increased nail fold width
  • Decreased nail thickness
  • Medial rotation of the toe
• Many others proposed; none proven, including the following:
  • Distorted, thickened nail (onychogryphosis)
  • Fungal infection (onychomycosis)
  • Hyperhidrosis
  • Improper trimming of the lateral nail plate
  • Poorly fitting shoes
  • Trauma to nail or nail fold
  • Conditions that predispose to pedal edema (i.e., thyroid dysfunction, diabetes, obesity, heart failure, renal disease)

General Prevention

• Properly fitting shoes
• Proper nail trimming (see “Patient Education”)