A case of Dravet syndrome complicated by human herpesvirus-6 infection-associated acute encephalopathy and choreoathetosis.

We report the case of a 14-month-old girl with Dravet syndrome carrying a splice-site mutation of c. 1170+1G>A on neuronal sodium channel alpha 1 subunit (SCN1A). She had a history of recurrent febrile or afebrile seizures since 4 months of age and developed acute encephalopathy due to infection with human herpesvirus-6, which presented with high grade fever, severe consciousness disturbances, and prolonged and clustered seizures. Electroencephalography showed a generalized slow activity. Intensive treatments, including mechanical ventilation, continuous thiopental infusion, and high-dose steroid therapy were initiated, and she gradually recovered. During the recovery phase, choreoathetosis-like involuntary movements appeared on the face and limbs, which were treated successfully with haloperidol. MRI findings during the acute phase were normal; however, diffuse cerebral atrophy became evident during the recovery phase. Single photon emission computed tomography (SPECT) of the brain revealed decreased cerebral perfusion over bilateral frontal and temporal lobes; however, perfusion of the occipital lobes, basal ganglia, and cerebellum remained normal. The patient showed serious developmental regression at discharge, with the loss of head control and meaningful words. Patient’s clinical course and the findings of SPECT resembled those of acute encephalopathy with biphasic seizures and late reduced diffusion (AESD), with the exception of lack of reduced diffusion of the subcortical white matter on the acute phase MRI and the prolonged and severe clinical symptoms. It has been reported that patients with Dravet syndrome are prone to complications, including various types of acute encephalopathies. Therefore, clinicians should carefully manage prolonged febrile seizures in patients with Dravet syndrome.