Standard treatment–refractory cytomegalovirus encephalitis unmasked by immune reconstitution inflammatory syndrome and successfully treated with virus‐specific hyperimmune globulin

Objectives Cytomegalovirus (CMV)‐related encephalitis is a rare but potentially life‐threatening complication of CMV infection in immunocompromised patients. The high mortality rate is associated with deficient immune system reconstitution after hematopoietic stem cell transplant (HSCT) and poor bioavailability of antiviral drugs in cerebrospinal fluid (CSF). CMV‐related central nervous system (CNS) infection may occur with aspecific symptoms, without evidence of either blood viral load or magnetic resonance imaging (MRI) signs of encephalitis. Methods Here, we describe a 10‐year‐old girl who underwent an allogeneic HSCT and subsequently developed CMV encephalitis. Because of the absence of CMV antigen in the blood, the diagnosis of encephalitis was proposed only after a delay, following the onset of immune reconstitution inflammatory syndrome (IRIS). Two months of combined dual antiviral therapy with ganciclovir and foscarnet proved ineffective against CMV and caused significant bone marrow and renal toxicity. To avoid further toxicity, the girl was given daily treatment with CMV‐hyperimmune globulins alone. Results After three weeks, the CSF viral load dropped significantly and was undetectable within three more weeks. In the meantime, the renal impairment resolved, and there was a complete bone marrow recovery. Conclusion We suggest that this patient succeeded in achieving CMV CSF clearance with high dose of CMV‐hyperimmune globulin, given alone, because of the ability of immunoglobulins to penetrate the blood–brain barrier (BBB).