Herpetic Whitlow

🩸 Herpetic whitlow is a painful viral infection of the finger caused by the Herpes simplex virus (HSV), usually HSV-1 (oral type) or HSV-2 (genital type). It presents with intense local pain, swelling, and vesicles around the nail or fingertip. Recognition is vital — incision or drainage is contraindicated as it can worsen infection and lead to viremia or bacterial superinfection.

🧠 About

• First described in healthcare workers, especially dentists and nurses, due to contact with patients’ oral secretions.
• Now also seen in children with orolabial herpes and adults with genital herpes (autoinoculation).
• Commonly affects the distal phalanx of the thumb or index finger.
• Can recur, particularly in immunocompromised individuals.

🧬 Aetiology

• Caused by Herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2).
• HSV infects the skin through small abrasions and travels via sensory nerves to the dorsal root ganglia where latency is established.
• Reactivation can occur with stress, trauma, or immunosuppression.

⚕️ Pathophysiology

• Primary infection → local viral replication in epidermal and dermal cells → vesicle formation.
• Inflammation produces swelling and severe pain due to confinement of the pulp space.
• Virus then enters sensory nerve endings → latent infection in the local ganglion → possible future recurrence.

🩺 Clinical Features

• Prodrome: Tingling, burning, or pain in the fingertip or periungual area before lesions appear.
• Lesions: Grouped, clear vesicles on an erythematous base — may become cloudy but should not be incised.
• Marked tenderness, swelling, and throbbing pain (often disproportionate to appearance).
• Regional lymphadenopathy, malaise, and low-grade fever may occur.
• Lesions crust and heal within 2–3 weeks without scarring.

🧪 Differential Diagnosis

• Bacterial paronychia/felon: More fluctuant, purulent, and without vesicles.
• Contact dermatitis or dyshidrotic eczema: Usually non-tender vesicles.
• Insect bite or burn blister: Single lesion, no prodrome.
• Varicella-zoster lesion: Often follows a dermatomal pattern.

🔬 Investigations

• Usually a clinical diagnosis — history and vesicular appearance are diagnostic.
• For confirmation or atypical cases:
  • Viral PCR or culture from vesicle fluid.
  • Tzanck smear (shows multinucleated giant cells, though nonspecific).
  • Serology (HSV antibodies) if recurrent or uncertain.

💊 Management

• Supportive treatment is usually sufficient.
• Antiviral therapy:
  • Aciclovir 400 mg TDS for 5–7 days, started early (<48 hrs) shortens duration and pain.
  • Alternatives: Valaciclovir 500 mg BD or Famciclovir 250 mg TDS.
• Analgesia: Paracetamol, ibuprofen, elevation of the hand.
• Local care: Keep clean, dry, and covered; avoid touching eyes or mucous membranes.
• Do NOT incise or drain the lesion — this may cause viral dissemination or bacterial superinfection.
• In immunocompromised patients or severe cases, consider IV aciclovir.

🧩 Prevention

• Use of gloves in healthcare settings — particularly during oral or genital examinations.
• Avoid direct contact with active herpes lesions.
• Educate patients with oral/genital herpes about autoinoculation risk (avoid touching sores).
• Recurrent cases may benefit from suppressive antiviral therapy (e.g. aciclovir 400 mg BD).

⚠️ Complications

• Secondary bacterial infection (usually staphylococcal).
• Autoinoculation to eyes (herpetic keratitis) — sight-threatening.
• Recurrence from latent virus in local ganglia.
• Disseminated HSV infection in immunocompromised or neonates.

📚 References

• BNF: Aciclovir
• UpToDate: “Herpetic Whitlow: Clinical features and management.”
• BMJ Best Practice: “Herpetic Whitlow.”
• Whitley RJ. N Engl J Med 2018; 378:171–179.