Cytokine storm of acute necrotizing encephalopathy.

Acute necrotizing encephalopathy is a rare, clinically distinct entity characterized by multiple, symmetric areas of edema and necrosis in the thalamus, cerebellum, brainstem, and white matter. It is postulated to arise from uncontrolled cytokine release during a febrile illness, and is most often seen in East Asia. We describe a rare North American case of acute necrotizing encephalopathy attributable to human herpes virus-6 is a 9-month-old white male. The infant moved to the United States from Hong Kong, 3 months before disease onset. A workup revealed elevations in serum interleukin-1β, interleukin-2, and interleukin-10, with normal values of interleukin-6 and tumor necrosis factor-α after the initiation of high-dose steroids. This profile is unique compared with previous cytokine profiles of this disease, possibly because of the effects of steroid therapy. A rare North American case with a history of birth in East Asia underscores the possibility of a role for environmental pathogens in this disease.