We report the clinical laboratory, electroencephalography (EEG), magnetic r
esonance imaging (MRI) and single photon emission computerized tomography (
SPECT) findings in a 15 year-old euthyroid girl with autoimmune thyroiditis
and encephalopathy. She had stupor, coma and generalized tonic clonic seiz
ure preceded by tremor and myoclonus with a previous misdiagnosis of epilep
sy and encephalitis. Response to steroid after the 3rd relapse was excellen
t. Another four children in the literature are also discussed.