Shingles, also known as herpes zoster, is a painful viral infection. It is caused by the varicella-zoster virus (VZV), the same virus responsible for chickenpox. After an initial chickenpox infection, VZV can remain inactive in the body’s nerve cells for many years. When reactivated, it produces a painful, blistering rash, often accompanied by itching or tingling.
The Typical Unilateral Presentation
Shingles commonly presents as a rash on one side of the body or face, forming a single stripe of blisters. This one-sided distribution occurs because the varicella-zoster virus lies dormant within sensory nerve clusters called ganglia, located near the spinal cord or at the base of the skull. When the virus reactivates, it travels along the nerve pathway from a single ganglion to the skin area supplied by that nerve. This area of skin is known as a dermatome, and the rash forms within it, typically appearing as a band or stripe that almost never crosses the midline of the body.
Understanding Bilateral Shingles
While shingles is almost always unilateral, it can, in rare instances, affect both sides of the body. This is known as bilateral shingles. It means the rash and blisters appear on dermatomes on both the left and right sides of the body. This bilateral presentation does not necessarily imply symmetry, nor does it mean the rash appears on both sides at the exact same time. The simultaneous reactivation of the virus in multiple ganglia on opposite sides of the body is uncommon, occurring in less than 1% of all shingles cases.
Factors Leading to Bilateral Shingles
Bilateral shingles often points to underlying conditions that compromise the immune system. A weakened immune response can allow the dormant varicella-zoster virus to reactivate in more than one sensory ganglion, or to spread more broadly. Conditions like HIV/AIDS, cancers, and organ transplantation are risk factors. Patients undergoing treatments like chemotherapy or taking immunosuppressive medications are also more susceptible. In these situations, the body’s immune defenses may be insufficient to contain the virus to a single nerve pathway, leading to involvement on both sides.
Clinical Importance of Bilateral Shingles
Bilateral shingles holds important clinical implications, as it frequently signals an underlying immune system compromise or systemic disease. Prompt medical evaluation is necessary to identify any undiagnosed conditions affecting the immune system. Physicians often investigate for conditions such as HIV, cancer, or other systemic disorders. While the rash is treated with antiviral medications like acyclovir, valacyclovir, or famciclovir, the primary focus for bilateral cases shifts toward diagnosing and managing the root cause of the immune suppression. Addressing the underlying condition is important for the patient’s overall health and to prevent further complications.