Herpetic Whitlow

A 34-year-old UTMB Pathology resident from Uzbekistan presents with a lesion on his middle finger (see image). He denies pain or other symptoms.

Which of the following is the most likely diagnosis?

A) Herpetic whitlow

B) Felon

C) Paronychia

D) Impetigo

E) Contact dermatitis

The correct answer is "Herpetic Whitlow"

Herpetic whitlow is a localized infection of the finger, typically caused by herpes simplex virus (HSV), most commonly HSV-1 but occasionally HSV-2. Here are key points about the condition:

• Etiology and Pathogenesis:
• The infection usually occurs when the virus enters through a break in the skin. It may result from autoinoculation (e.g., touching a cold sore and then touching the finger) or through direct contact with infected secretions. Once the virus enters the epidermis, it replicates, causing cytopathic changes.
• Clinical Presentation:
• The classic appearance includes grouped vesicles on an erythematous base. While the condition is often painful, some cases, like the one in the question, might be relatively asymptomatic. Other symptoms may include swelling and sometimes a mild fever, but systemic symptoms are uncommon.
• Diagnosis:
• Diagnosis is usually clinical, based on the characteristic appearance of the lesion and patient history. Laboratory confirmation can be obtained using viral culture, polymerase chain reaction (PCR), or Tzanck smear (which reveals multinucleated giant cells), although these tests are less frequently needed.
• Differential Diagnosis:
• It is important to differentiate herpetic whitlow from bacterial infections such as felon or paronychia, which typically present with more localized pain, purulent discharge, or more diffuse inflammation. Impetigo and contact dermatitis are also considered in the differential but have distinct features.
• Treatment:
• Management typically involves antiviral therapy (e.g., acyclovir) to reduce the duration of symptoms and viral shedding. Pain management may also be necessary. In most cases, the condition is self-limiting, but recurrent infections can occur due to viral latency in nerve ganglia.
• Prevention:
• Preventive measures include avoiding contact with active herpes lesions, particularly for healthcare workers and others at risk, and practicing good hand hygiene to prevent autoinoculation.

Other options

Felon is a deep-seated infection of the fingertip pulp that usually presents with severe pain and swelling.

Paronychia affects the nail folds and is associated with redness, swelling, and tenderness around the nail.

Impetigo is a superficial bacterial infection, commonly seen in children, characterized by honey-colored crusts.

Contact dermatitis is an inflammatory reaction due to irritants or allergens, often presenting with itching and a more diffuse rash rather than grouped vesicles.

Good luck =)