A patient with fever and unilateral dermatomal rash along an intercostal space is most consistent with which diagnosis?

• A. Gastroenteritis.
• B. Meningitis.
• C. Shingles.
• D. Lupus flare.

Answer: (C)

A unilateral, dermatomal rash along an intercostal space is classic for shingles, which is reactivation of the varicella-zoster virus in a dorsal root ganglion. The virus travels along sensory nerves to the skin, producing a band of vesicular lesions that aligns with a single dermatome and typically stays on one side of the body. The thoracic region is a common site, and patients may first notice localized pain or burning before the rash appears. Fever can be present but isn’t the defining feature; the key clue is the belt-shaped, unilateral dermatomal distribution.

This pattern doesn’t fit the other conditions: gastroenteritis would present with gastrointestinal symptoms like vomiting and diarrhea; meningitis would involve headache, neck stiffness, photophobia, and altered mental status rather than a dermatomal rash; a lupus flare would show systemic symptoms and different rash patterns (such as a malar rash) rather than a single dermatomal belt.

Early antiviral treatment within about 72 hours of rash onset improves outcomes and lowers the risk of postherpetic neuralgia, especially in older adults.