Can shingles present bilaterally on the flanks?

Shingles Presentation on Bilateral Flanks

Shingles (herpes zoster) typically presents as a unilateral vesicular eruption in a dermatomal distribution and bilateral presentation on the flanks is atypical but can occur in immunocompromised patients or in cases of disseminated zoster infection 1.

Typical Presentation of Shingles

• Herpes zoster classically presents with a unilateral vesicular eruption following a dermatomal distribution 1
• The rash is usually preceded by prodromal pain that occurs 24-72 hours before skin findings appear 1
• Lesions progress from erythematous macules to papules and then to vesicles, continuing to erupt for 4-6 days in immunocompetent hosts 1
• The total disease duration is approximately 2 weeks in otherwise healthy individuals 1
• The distinctive sign is a vesicular dermatomal rash or ulceration, typically affecting one side of the body 2

Atypical Presentations

• While herpes zoster is typically unilateral, it can present bilaterally in certain circumstances 2
• Immunocompromised patients may develop more extensive disease with atypical presentations, including bilateral involvement 3, 1
• Recipients of blood, bone marrow, or solid organ transplants are at higher risk for developing atypical herpes zoster presentations 1
• In immunocompromised hosts, skin lesions may continue to develop over a longer period and generally heal more slowly 4
• Disseminated zoster (defined as >20 lesions outside the primary and adjacent dermatomes) can present with bilateral involvement 3

Diagnostic Considerations

• Clinical diagnosis of bilateral shingles should prompt consideration of immune status evaluation 1
• Laboratory confirmation is essential for atypical presentations, with viral culture, PCR, or antigen detection being available methods 4
• Consider alternative diagnoses that may mimic herpes zoster, especially when the presentation is bilateral 1
• Tzanck smear showing giant cells can be diagnostic for herpesvirus infection 1
• Vesicle fluid specimens can be obtained for immunofluorescence antigen testing, culture, or PCR to confirm diagnosis 1

Management Implications

• For uncomplicated herpes zoster, oral acyclovir or valacyclovir are the recommended first-line treatments 3
• For disseminated or invasive herpes zoster (which may present bilaterally), intravenous acyclovir is recommended 3
• In immunocompromised patients with disseminated disease, temporary reduction in immunosuppressive medication should be considered alongside antiviral therapy 3
• High-dose IV acyclovir remains the treatment of choice for VZV infections in severely compromised hosts 3
• Treatment should be continued until all lesions have scabbed 3

Clinical Pitfalls and Caveats

• Bilateral presentation should raise suspicion for an immunocompromised state or disseminated disease 1
• Lack of typical dermatomal distribution may lead to delayed diagnosis and treatment 5
• Secondary bacterial and fungal superinfections can occur, particularly in immunocompromised hosts with atypical presentations 1
• Topical antiviral therapy is substantially less effective than systemic therapy and is not recommended 3
• Bilateral presentation may be confused with other vesicular eruptions, emphasizing the importance of laboratory confirmation in atypical cases 4