• Clinical science

Finger infections

Abstract

Common finger infections include paronychia, felon, and herpetic whitlow. A paronychia is an acute or chronic soft tissue infection around the nail body. Acute infections are typically bacterial in origin and usually occur after minor trauma. Chronic paronychia infections have a multifactorial etiology, often related to repeated exposure to moist environments and/or skin irritants, and may be accompanied by secondary fungal infection. The diagnosis of paronychia is based on clinical signs of inflammation. A bacterial culture or fungal stain can confirm the causative pathogen. Treatment of acute paronychia usually involves antibiotics, while chronic paronychia is treated with topical steroids and antifungal therapy. Complications include nail dystrophy or felon.

Felon is an infection of the distal pulp space of the fingertip. While the cause is often unknown, minor trauma most commonly precedes infection. It is a clinical diagnosis based on the presence of local pain, swelling, induration, and erythema. Early stages of felon may be managed conservatively with analgesics and antibiotics. Later stages require incision and drainage. Complications include fingertip soft tissue necrosis and osteomyelitis.

Herpetic whitlow is discussed in herpes simplex virus infections.

Paronychia

  • Definition: soft tissue infection around a fingernail
  • Epidemiology
    • Most common hand infection in the United States
    • Sex: > (3:1)
Acute Chronic
Etiology
  • Multifactorial: chronic exposure to moist environments or skin irritants (e.g., household chemicals) → eczematous inflammatory reaction → possible secondary fungal infection
  • Particularly in immunocompromised individuals (e.g., HIV-positive)
Clinical features
  • Chronic or episodic history > 6 weeks of inflamed posterior and lateral nail folds without fluctuance
  • May progress to thick, discolored nail plates → separation of cuticles/nail folds from the nail plate
Diagnosis
  • Clinical diagnosis
  • Gram stain/culture to identify pathogen
  • KOH smear if gram stain is negative or a chronic fungal infection is suspected
  • X-ray if osteomyelitis or a foreign body is suspected
Treatment
  • If caught early and without fluctuance: elevation and warm soaks 3–4 times daily
  • Antibiotics (e.g., amoxicillin-clavulanate) if infection is extensive or if the patient is immunocompromised
  • Surgical drainage if abscess is present: no-incision technique, simple incision technique, single and double-incision techniques
  • Avoid skin irritants, moisture, and mechanical manipulation of the nail
  • Topical steroids (e.g., methylprednisolone)
  • Consider antifungal: topical (e.g., miconazole); oral (e.g., fluconazole) if severe
  • Surgical drainage if abscess is present: eponychial marsupialization
Complications

References:[1][2][3][4]

Felon

  • Definition: distal pulp space infection of the fingertip
  • Etiology
  • Clinical features
    • Commonly involves the thumb and index finger
    • Localized edema at the fingertip; associated with pressure, prickling, or throbbing pain
  • Diagnosis
    • Clinical diagnosis
    • Culture wound fluid: to identify the causative pathogen
    • Imaging (e.g., x-ray) if osteomyelitis or a foreign body is suspected
  • Treatment
    • Early oral antibiotic treatment, decompression , and elevation should improve the condition in 12–24 hours.
    • Tetanus prophylaxis
    • If severe or blood flow is compromised: IV antibiotics and surgical drainage
  • Complications: necrosis, osteomyelitis, tenosynovitis, septic arthritis

References:[5][6]

Blistering distal dactylitis

  • Definition: bacterial infection of the distal periungual tissue
  • Etiology: infection with group A hemolytic streptococci; less commonly also with Staphylococcus aureus
  • Clinical features
    • Development of a single, purulent blister (1–2 cm)
    • Located on the anterior palmar fat pad near the nail folds
  • Diagnosis: Gram stain of blister contents shows gram-positive cocci.
  • Treatment: incision and drainage + oral antibiotics
  • Complications: separation of nail from the nail bed; permanent nail dystrophy