Diagnostic Confirmation of HSV in a Patient on Chronic Suppressive Therapy
Obtain viral culture or PCR from the perianal lesions to confirm HSV reactivation, as clinical diagnosis alone is insufficient to justify continued acyclovir prescription, especially given the atypical presentation of pruritus rather than pain. 1
Why Diagnostic Testing is Essential in This Case
Your patient presents with an atypical clinical picture that requires laboratory confirmation before continuing therapy:
- Pruritic (not painful) perianal lesions are atypical for HSV, which classically presents with painful vesicles and ulcerations 2
- The patient has been on suppressive therapy for 6 years, which should reduce recurrence frequency by ≥75% 3
- Breakthrough lesions on adequate suppressive therapy (400 mg BID) warrant investigation for alternative diagnoses or potential acyclovir resistance 1
Recommended Diagnostic Approach
Viral identification methods (in order of preference):
- PCR or viral culture with immunofluorescence from the lesion base or vesicular fluid if any vesicles are present 2
- Immunohistochemistry on skin biopsy if lesions are ulcerated and no vesicular fluid is available for culture 2
- Histology alone is only suggestive (positive in 2 of 5 cases in one study) and requires viral confirmation 2
Critical Differential Considerations
The pruritic nature of these perianal lesions raises important alternative diagnoses:
- Fungal infections (candidiasis, dermatophytosis) are common in the perianal region and present with pruritus 2
- Bacterial infections can mimic HSV in this location 2
- These conditions were confused with HSV for 10-14 days in bedridden patients with actual herpetic lesions, highlighting diagnostic difficulty 2
What to Look for on Physical Examination
Classic HSV features (if present, increase diagnostic confidence):
- Well-demarcated, painful ulcerations (not pruritic) 2
- Grouped vesicles on an erythematous base (early lesions) 1
- Inguinal lymphadenopathy may or may not be present 2
Atypical features requiring broader workup:
- Pruritus as the dominant symptom suggests non-herpetic etiology
- Absence of pain is unusual for HSV 2
- Prolonged time course without typical vesicular progression 2
Implications for Continued Acyclovir Therapy
If HSV is confirmed:
- Continue acyclovir 400 mg BID, as this regimen is safe and effective for up to 6 years of continuous use 3
- Consider that after 6 years, you should discuss discontinuation to reassess the patient's natural recurrence rate 3
- If lesions persist despite adequate dosing, suspect acyclovir resistance and consider consultation for alternative therapy (foscarnet or cidofovir) 1
If HSV is not confirmed:
- Discontinue acyclovir and treat the actual underlying condition (antifungal for candidiasis, antibacterial for bacterial infection, etc.)
- The pruritic presentation strongly suggests this scenario
Common Pitfall to Avoid
Do not assume all perianal lesions in a patient with HSV history are herpetic recurrences. Even in patients with documented HSV, perianal lesions were misdiagnosed as fungal or bacterial infections for 10-14 days before correct viral identification 2. The pruritic rather than painful nature of your patient's lesions makes alternative diagnoses more likely than HSV breakthrough.