An adult case of pandemic (H1N1) 2009 influenza associated encephalopathy

A healthy 40-year-old man was admitted to our hospital because of impaired consciousness and convulsions starting five days after a high fever. Though rapid influenza diagnostic tests were negative, RT-PCR assay detected influenza A (H1N1) 2009 viral RNA from nasopharyngeal swab specimens. Initially high concentrations of interleukin-6 (IL-6) in serum and cerebrospinal fluid decreased as the symptoms improved, as with past influenza-associated encephalopathy cases. Scattered high signal intensity lesions in the cerebral cortex and right medial thalamus on magnetic resonance imaging (MRI) disappeared, and diffuse brain atrophy remained. It is necessary to be aware of the possibility of healthy adults developing pandemic 2009 influenza A (H1N1)-associated encephalopathy and that rapid influenza diagnostic tests have limited accuracy.