What is Whitlow
Whitlow, specifically herpetic whitlow, is a painful viral infection of the fingers or toes caused by herpes simplex virus (HSV) type 1 or type 2, characterized by vesicles, erythema, swelling, and tenderness of the distal phalanx. 1, 2
Clinical Presentation
Key diagnostic features include:
- Sensory prodrome (itching, burning, tingling, or paresthesia) that precedes visible lesions by hours 1
- Vesicles with clear fluid that may coalesce into bullae, typically appearing honeycomb-like 1, 2
- Significant pain and erythema with overlying nonpurulent vesicles 3
- Swelling and tenderness of the affected digit, often involving the nail folds 2, 4
- Vesicles burst to form shallow ulcers or erosions 1
- May present with fever and swollen lymph nodes 5
The infection typically affects the distal phalanx of fingers or toes, though atypical locations like the palm have been reported 6. In pediatric populations, it commonly occurs on fingers and toes due to autoinoculation from oral secretions, particularly in children who bite their nails 2, 6.
Pathophysiology and Transmission
The virus infects the digit through direct inoculation, establishing the characteristic localized infection 2. Healthcare workers with orofacial herpes lesions should be restricted from direct care of newborn infants until lesions are crusted to prevent transmission 7.
Diagnostic Challenges and Pitfalls
Critical diagnostic confusion occurs because herpetic whitlow mimics several other conditions:
- Bacterial paronychia - the most common misdiagnosis 2
- Flexor tenosynovitis - can present with positive Kanavel's cardinal signs, leading to unnecessary surgical intervention 3
- Bacterial cellulitis or abscess - may appear abscess-like with surrounding erythema 2, 6
- Embolic disease 2
Laboratory confirmation is essential because clinical diagnosis alone is unreliable 1. The proper diagnostic approach includes:
- Viral culture for HSV 2, 3
- PCR testing (most sensitive method) for HSV-1 and HSV-2 1, 4
- Note that initial PCR may be negative and require repeat testing 4
Common pitfall: Improper diagnosis frequently leads to unnecessary antibiotic therapy, extensive work-up, or even surgical incision and drainage, which is contraindicated 2, 6, 3.
Special Populations
In immunocompromised patients (including HIV-positive individuals):
- Lesions are more severe, extensive, and non-healing 1
- Prolonged viral shedding occurs 1
- May develop resistant HSV infection requiring alternative antiviral therapy like foscarnet 4
- Episodes are longer and more severe 1
Clinical Course and Management Considerations
The infection is typically self-limiting in immunocompetent individuals, lasting less than 10 days 1. However, the cycle may be prolonged by:
- Secondary bacterial infection (which cannot always be excluded, especially with associated lymphangitis) 2, 6
- Immunosuppression 1
Recurrences typically occur at the same site as the primary infection 1, and patients may experience recurrent episodes over years 4, 3.
Peak viral titers occur within the first 24 hours after lesion onset when most lesions are vesicular 1, making early recognition crucial for appropriate management and infection control.