Pearls & Oy-sters: Seronegative Eastern Equine Encephalitis in an Immunocompromised Stem Cell Transplant Recipient

Altered mental status in immunosuppressed patients has a wide differential diagnosis. In this case, a 27-year-old man presented with encephalopathy, nausea, vomiting, and fevers. His medical history was significant for acute myeloid leukemia in remission after allogenic hematopoietic stem cell transplantation 17 months prior complicated by graft vs host disease affecting his skin treated with sirolimus. A lumbar puncture was performed with a lymphocytic pleocytosis, mildly elevated protein, and negative Gram-stain and bacterial and fungal cultures. His examination deteriorated, and he became comatose with loss of pupillary and corneal reflexes. An MRI of his brain demonstrated T2/fluid-attenuated inversion recovery signal abnormality involving the bilateral basal ganglia, mesial temporal lobes, and entire brainstem along with bilateral temporal parenchymal and leptomeningeal enhancement. Ultimately, diagnosis was made through metagenomic PCR sequencing from his CSF. This case highlights diagnostic challenges in immunosuppressed patients because antibodies against the causative antigen were negative (potentially related to decreased antibody production in the setting of immunosuppression).