La Crosse encephalitis presenting like herpes simplex encephalitis in an immunocompromised adult.

The diagnosis of the precise cause of viral encephalitis can be difficult, hampered by the nonspecific presentation, the number of etiologic viruses, and limited culture and serologic diagnostic methods. Because herpes simplex encephalitis (HSE) can be neurologically devastating and is treatable, timely diagnosis is important. We report an immunocompromised adult with encephalitis clinically consistent with HSE who had serology consistent with recent La Crosse encephalitis (LAC).