Michiya Omi, Daisuke Watanabe, Takuya Takeichi
Very rarely, live attenuated varicella zoster virus (VZV) vaccine recipients develop herpes zoster (HZ) without a preceding history of clinical varicella. A 14-month-old girl without prior varicella developed vesicles on her right arm and back. She received zoster vaccine live (ZVL) on the right arm 65 days earlier. A rapid immunochromatographic VZV antigen detection kit (DermaQuick VZV, Maruho, Osaka, Japan) was positive. Because PCR strain typing was not performed, the causative agent could not be definitively identified as the vaccine strain; therefore, breakthrough varicella or HZ due to wild-type VZV could not be completely ruled out. Based on the clinical and laboratory findings, she was diagnosed with HZ. Weight-adjusted oral valacyclovir was initiated at 200 mg four times daily for seven days. At seven-day follow-up, the vesicles had resolved into erythema and erythematous papules accompanied by desquamation in some areas. Assuming the HZ in our current case originated from the ZVL strain, it is hypothesized that the administered virus replicated locally in the skin, traveled retrogradely via sensory nerves to establish latency, and subsequently reactivated to cause HZ in the dermatome that corresponded to the injection site. Clinicians should include HZ in the differential diagnosis when they encounter a unilateral vesicular eruption in an immunocompetent infant with no history of varicella. DermaQuick, a simple and minimally invasive method, is extremely useful for rapidly diagnosing such cases.