This Literature - Spontaneous case, initially received on 14-Feb-2017, was reported by a health professional and concerns an 18-month-old male patient. Weight: not provided; Height: not provided. Drug history included Varicella-zoster virus (VZV) vaccine and routine vaccines (fully vaccinated) at 12 months of age administered in the left thigh. Concomitant medication: not reported. Administration of company suspect drug(s): On an unknown date, the patient received Influenza Virus Vaccine (INN) for indication not reported. Dose regimen: Not reported, Route of administration: Not Reported. Batch number: Not reported. Site: Left buttock. No additional suspect drugs. Adverse reactions/events and outcomes: On an unknown date, drug administered to patient of inappropriate age (outcome: not reported). Special circumstances: drug administered to patient of inappropriate age. On an unknown date one week following vaccination, the patient was uncomfortable when getting dressed (outcome: recovering/resolving). On an unknown date one week following vaccination, the patient experienced Herpes zoster (medically significant, outcome: recovering/resolving). Associated symptoms included: Erythema scattered across the left buttock, thigh, and upper calf, some with central punctate hemorrhagic crust, Multiple discrete clusters of monomorphic pink to violaceous scattered across the left buttock, thigh, and upper calf, Patch became raised and spread down the left thigh and Red patch near the site of vaccination. The influenza vaccine was administered 1 week prior to presentation in the left buttock, after which his parents noted a red patch near the site of vaccination. The patch became raised and spread down the left thigh over the course of several days. The rash did not bleed, ulcerate, weep, or appear itchy or painful, though the patient did seem uncomfortable when getting dressed. He had no known sick contacts at day care, exposure to herpes simplex virus, or exposure to new topical products or clothing. His pediatrician prescribed cephalexin and mupirocin for a presumed cutaneous bacterial infection. The eruption continued to spread down his left thigh over the next 2 days, at which point the pediatrician advised the family to go to the emergency department. On examination, the boy was afebrile and well-appearing. There were multiple discrete clusters of monomorphic pink to violaceous papulovesicles with surrounding erythema scattered across the left buttock, thigh, and upper calf, some with central punctate hemorrhagic crust. The lesions were nontender. There were no skin lesions elsewhere. A test was performed. Diagnosis: Herpes zoster. The grouped papulovesicles in a unilateral L3-L5 distribution involving the same extremity in which the varicella-zoster virus (VZV) vaccine was administered raised suspicion for herpes zoster in this patient. Direct fluorescent antibody of a vesicle confirmed the presence of VZV. Because the patient's eruption was asymptomatic and improving by the time that test results were available, treatment with acyclovir was deferred. Reporter's Comments: Reporter's assessment: The morphology of our patient's eruption raised concern for a microcystic lymphatic malformation (lymphangioma circumscriptum), which is a benign congenital malformation of dilated superficial lymphatic vessels leading to monomorphic pseudovesicles (appearing to contain clear fluid). Often described as "frog spawn" in appearance. While lymphatic malformations can become more prominent after trauma, such as vaccination, the acute time course of this patient's eruption with no precursor lesion reduced the likelihood of lymphatic malformation. Varicella-zoster virus reactivation resulting in herpes zoster is a well-described, but uncommon occurrence in healthy children immunized with live attenuated varicella vaccine. Risk factors for herpes zoster include receipt of any vaccination within 30 days prior to symptom onset and race. Sender's Comments: Listedness: Brand of Influenza vaccine not specified. Assessment according to CCSI for CSL's Inactivated Influenza Virus Vaccine, Herpes zoster and Drug administered to patient of inappropriate age are unlisted. Causality: Related. Time to onset is 1 week following Influenza vaccination. The infant received Varicella-zoster vaccine at 12 months. Zoster (reactivation) can occur in healthy infants/children, any time after administration of live Varicella-zoster vaccine. Influenza vaccination is not implicated in reactivation of the latent varicella zoster virus. Causality is therefore considered not related despite the temporal association.