Abstract: Successful desensitization to acyclovir has been reported in the past but not to valganciclovir. This is the first successful desensitization to valganciclovir in a liver transplant recipient. Valganciclovir—a nucleoside analogue antiviral drug—is the drug of choice for treatment of cytomegalovirus (CMV) disease and prophylaxis in high-risk liver transplant recipients (1). Nucleoside analogues including acyclovir, famciclovir, and ganciclovir are known to cause immediate hypersensitivity cutaneous reactions. In case of allergic reactions to nucleoside analogues or acyclovir-resistant herpes infections, sodium—a DNA chain inhibitor of phosphorylation—may be used as an alternative, although it may cause nephrotoxicity. We report a successful desensitization to valganciclovir in a liver transplant recipient with CMV infection. A 64-year-old patient with a history of liver transplant caused by hepatocellular carcinoma presented with fatigue and anorexia 1 month after his transplant. Both, recipient and donor were CMV positive. The patient was diagnosed with CMV viremia by polymerase chain reaction and was started on valganciclovir. He developed a generalized pruritic urticaria on his trunk and upper extremities without other symptoms on the fourth day of therapy. There was a concern for drug reaction with eosinophilia and systemic symptoms syndrome because of increased peripheral eosinophil with an eosinophil count of 8.1% (range, 0%–3%). Skin biopsy was not performed. The patient's rash improved after use of antihistamines and discontinuation of valganciclovir. The use of sodium as an alternative failed because of acute renal toxicity with a serum creatinine of 2.2 mg/dL (baseline, 1.3; range, 0.7–1.3). Allergy and immunology was consulted for desensitization to valgan ciclovir. Skin testing was not performed because of concomitant use of antihistamines for severe pruritus and urticaria. We designed a novel 12-step desensitization protocol (Table 1) adapted from previous recommended guidelines (2, 3). In an intensive care unit setting and use of prior medications (diphenhydramine 25 mg intravenous and famotidine 20 mg intravenous), oral desensitization with valganciclovir was performed. He completed the desensitization protocol without adverse reactions. Within days, the patient's serum creatinine and eosinophil count normalized to 1.3 mg/dL and 0.2%, respectively. The patient completed a 2-week induction therapy with valganciclovir 450 mg twice per day without further reactions and is currently on lifetime valganciclovir 450 mg once daily.TABLE 1: Valganciclovir desensitization protocolThere are three previous reports of successful desensitization to acyclovir (4–6). We report the first successful desensitization to valganciclovir. Alexei Gonzalez-Estrada James Fernandez Department of Allergy and Clinical Immunology Cleveland Clinic, Cleveland OH