Introduction Narcolepsy often begins in childhood (30% of cases) but only around 4% are diagnosed before age 15. It is usually a slowly progressive disease, with mild symptoms. We report a case of an acute and florid narcolepsy in a 6-year-old diagnosed following an auto-immune encephalitis.

Case report A boy aged 6 presented with a 6-week history of excessive sleepiness and mild encephalopathy. An EEG showed a slow background c/w encephalopathy. Encephalitis Lethargica or another autoimmune encephalopathy was considered and he was treated with Methyl prednisolone, IVIG, high dose steroids with little improvement. CSF inflammatory markers, MRI brain and autoimmune screen were normal. He had positive ASOT and anti basal ganglia antibodies. He subsequently developed the tetrad of excessive sleepiness, cataplexy (many times a day), hallucinatory phenomena, and sleep paralysis and the psychosocial problems associated with narcolepsy. He is positive for HLA DQB1*0602. CSF analysis revealed low Hypocretin. His MSLT showed a median sleep of 55 s but no sleep onset REM. Daytime sleepiness has improved with methylphenidate but cataplexy remains difficult to treat.

Conclusion Encephalopathy has not been reported in narcolepsy. We would like to hypothesise that an auto-immune aetiology may be the underlying mechanism of this rapidly progressive explosive and florid narcolepsy.