Can Shingles Occur Bilaterally?
Yes, shingles can involve both sides of the body, though this is uncommon and represents an atypical presentation called "zoster bilateralis" or multidermatomal herpes zoster.
Typical Presentation vs. Bilateral Disease
The classic presentation of herpes zoster is unilateral, affecting a single dermatome on one side of the body. The disease manifests as a painful cutaneous eruption in a dermatomal distribution, with thoracic dermatomes being most common (40-50% of cases), followed by cranial nerve, cervical, lumbar, and sacral distributions 1. The unilateral, dermatomal pattern is the hallmark that distinguishes shingles from other vesicular eruptions.
However, bilateral or multidermatomal involvement does occur:
- Multidermatomal herpes zoster is characterized by rash spread over two or more adjacent or noncontiguous dermatomes, and can affect both sides of the body 2
- Cases involving multiple disparate dermatomes (up to 7 separate dermatomes) have been documented, including both unilateral and bilateral presentations 3
- This atypical presentation is referred to as "zoster duplex unilateralis" when affecting one side in multiple dermatomes, or "zoster duplex bilateralis" when both halves of the body are involved 3
Risk Factors for Bilateral/Multidermatomal Disease
Bilateral or multidermatomal herpes zoster occurs most commonly in immunocompromised patients, though it can rarely occur in immunocompetent individuals:
- HIV-infected patients have a >15-fold higher incidence of herpes zoster compared to age-matched controls, with highest frequency at CD4+ counts <200 cells/µL 1
- Cutaneous dissemination occurs in 25-50% of HIV-infected patients, and most herpes zoster complications occur with CD4+ counts <200 cells/µL 1
- Multidermatomal involvement has been documented in immunocompetent adults, though this is rare and diagnostically challenging 2
Clinical Pitfalls and Diagnostic Considerations
The key diagnostic challenge is that bilateral or multidermatomal presentations may be misdiagnosed as other conditions:
- Initial presentations may be mistaken for allergic reactions, drug hypersensitivity, or other dermatologic conditions 2
- Laboratory confirmation should be sought when the clinical presentation is atypical, including vesicular fluid collection for viral testing 4
- The diagnosis may be delayed because clinicians expect the classic unilateral dermatomal pattern 2
When evaluating suspected bilateral shingles, look for:
- Vesicles containing clear fluid that burst to form shallow ulcers or erosions 4
- Painful prodrome preceding the eruption (though pain may be absent in elderly patients) 5
- New vesicle formation continuing for 3-5 days, followed by pustulation and scabbing 1
- History of immunosuppression or HIV infection 1
Management Implications
Treatment approach remains the same regardless of unilateral or bilateral presentation:
- Antiviral therapy (valacyclovir or famciclovir preferred) should be initiated within 72 hours of onset 6
- Immunocompromised patients require particular attention due to higher risk of complications and dissemination 1, 6
- Post-herpetic neuralgia occurs in approximately 10-15% of HIV-seropositive patients and should be anticipated 1