Abstract
Epstein-Barr virus usually leads to mild, self-limiting infection in immunocompetent host. However, patients with defective cell-mediated cytotoxicity can get life-threatening infection with Hemophagocytic Lymphohistiocytosis features.
2-year-old Hispanic girl presented with acute onset of ataxia and slurry speech. No fever or lymphadenopathy were noted. CSF EBV PCR was positive and her MRI was consistent with viral encephalitis. She was treated with IVIG, steroids, and Acyclovir for 2 weeks. Over the next few months, her symptoms started to worsen again to the point that she could not sit up. Her MRI showed worsening of the inflammation with new hemorrhagic lesions. Brain biopsy was positive EBV DNA in situ hybridization and showed T cell and histiocytic infiltration. Her immunological evaluation revealed a mild reduction in T and NK cells number, normal B cells count, and normal immunoglobulin levels. HIV PCR was negative. SAP expression was normal; however, NK cell function was absent. HLH evaluation was unremarkable except for elevated serum and CSF neopterin levels. She was treated with steroid in addition to rituximab (IV and then intrathecally) to decrease the EBV viral load (fig1). Few weeks later, the Genetic test revealed a missense homozygotic mutation of perforin gene (c.1337A>C) which is validated by flow cytometry. With a diagnosis of primary HLH confirmed, the patient was treated with etoposide waiting for matched donor bone marrow transplant.
NK cells disorders should be considered in pediatric patients with severe or unusual EBV infection. Rituximab is effective in decreasing EBV viral load.