Snapshot A 19-year-old man presents to the emergency department for worsening malaise, fatigue, and arthralgias. His symptoms have been progressively worsening over the course of 5 days. He had an allograft renal transplant and is currently on tacrolimus. The patient denies any headache, cough, shortness of breath, or abdominal pain. He denies any recent travel or sick contacts. His temperature is 102°F (38.9°C), blood pressure is 105/78 mmHg, pulse is 92/min, and respirations are 17/min. Physical examination is unremarkable. Serological studies and blood cultures are obtained. Polymerase chain reaction returns positive for cytomegalovirus DNA. He is started on ganciclovir. Introduction Mechanism of action guanosine analog that is phosphorylated by a viral kinase into ganciclovir triphosphate ganciclovir triphosphate competitively inhibits the incorporation of deoxyguanosine triphosphate into DNA preferentially inhibits viral DNA polymerases Mechanism of resistance altered viral kinase Clinical use cytomegalovirus Adverse effects bone marrow suppression causing hematologic abnormalities neutropenia thrombocytopenia anemia nephrotoxicity