Herpetic Whitlow

Herpetic whitlow is infection of the distal finger or thumb with herpes simplex virus, either HSV-1 (more common in children, often from autoinoculation with oral HSV, or in healthcare workers from occupational exposure to oral or genital secretions before universal glove use became standard practice) or HSV-2 (more common in adults, typically from autoinoculation from genital lesions).

A prodrome of tingling or burning pain in the affected digit precedes the appearance of grouped, clear vesicles on an erythematous base, which may coalesce, and can be mistaken for a bacterial felon or paronychia, an important distinction given the very different management (incision and drainage is harmful in herpetic whitlow).

Associated lymphangitic streaking and tender epitrochlear or axillary lymphadenopathy are common.

Systemic symptoms (fever, malaise) may accompany a primary episode.

Lesions typically resolve over 2 to 3 weeks even without treatment, but recurrence from viral latency in the local sensory ganglion is common.

Primarily clinical, based on the characteristic vesicular appearance and prodrome.

Where confirmation is needed, PCR of vesicle fluid is the most sensitive test; viral culture and direct fluorescent antibody testing are alternatives.

Distinguishing from a bacterial felon is essential: herpetic whitlow lesions are typically grouped vesicles rather than a single area of purulent fluctuance, and Tzanck smear (though largely superseded by PCR where available) can show multinucleated giant cells supporting a herpetic cause.

• Aciclovir 400 mg PO tds for 7 to 10 days, or valaciclovir 1 g PO bd for 7 to 10 days, most effective if started within 48 hours of symptom onset, particularly for a primary episode; benefit is more modest for recurrent episodes given their typically shorter, self-limiting course
• Incision and drainage should be avoided, since this does not shorten the disease course, risks secondary bacterial infection, and can facilitate viral spread or, rarely, herpetic encephalitis via disruption of normal tissue barriers
• Keep the lesion covered to reduce autoinoculation risk to other sites (particularly the eye, given the risk of herpetic keratitis) and to reduce transmission to others
• Frequent recurrence (more than 4 to 6 episodes per year) may warrant suppressive therapy (aciclovir 400 mg PO bd, or valaciclovir 500 mg PO od, continued long term), following similar principles to suppressive therapy for genital herpes

Referral: dermatology or infectious disease for diagnostic uncertainty or frequent recurrence; occupational health assessment for healthcare workers with occupationally acquired disease.