Introduction Autoimmune encephalitis associated with N-methyl-d-aspartate (NMDA) receptor antibodies is increasingly recognised in intensive care but there have been no reports of recurrent cases.

Case A 22-year-old woman presented with in 2001 with generalised tonic clonic seizures followed by a progressive encephalopathy with confusion, fluctuating consciousness and impaired memory. Routine blood tests, auto-immune screen and serology were negative, CSF examination showed a pleocytosis and MRI revealed atrophy of the left hippocampus. She had a prolonged illness but made a slow recovery, returning to her premorbid level of functioning. She continued to suffer occasional seizures. She had a similar illness 13 years previously at the age of nine with encephalopathy, abdominal pain, headache, confusion and a hyperkinetic movement disorder. She again had made a slow but full recovery. No definitive cause for her illness had been found. Following reports of NMDA receptor encephalitis in 2008, this patient's serum tested positive for antibodies to the NMDA receptor. This confirmed the likely diagnosis of anti-NMDA receptor encephalitis.

Conclusion NMDA receptor encephalitis may develop in childhood and be recurrent. It can be useful to retrospectively test serum for antibodies in cases of undiagnosed encephalopathic illnesses.