Voltage gated potassium channel antibodies positive autoimmune encephalopathy in a child: A case report and literature review of an under-recognized condition
A 13-year-old, right handed, previously fit and healthy girl presented with a short history of generalised headaches and confusion. She had “flu-like” symptoms 4 weeks ago followed by complete recovery. There was no history of fever, drug ingestion, head injury, rash, tick bite or travel outside the country within last 6 months. Parents were non-consanguineous, Afro-Caribbean origin, and her father died at the age of 55 years from a “possible stroke.”\nOn admission, Glasgow Coma Scale was 13/15 and she was aggressive and disorientated. She was apyrexial with normal blood pressure and heart rate. There were no focal neurological signs, and general examination was unremarkable. Soon after admission she developed left focal motor seizures with secondary generalization, requiring intensive care treatment for the next 3 weeks. Seizures were difficult to control, and she had repeated episodes of status epilepticus, requiring multiple anticonvulsants. Repeated electroencephalogram (EEG) showed diffuse generalised slowing with no epileptiform discharges.\nInitial blood investigations were unremarkable, including full blood count and peripheral smear, baseline electrolytes, renal, liver and bone profile, haemoglobin electrophoresis, peripheral blood film for malarial parasites, investigations for tuberculosis, antibodies for Borrellia burgdorferi and human immunodeficiency virus. Highest C-reactive protein was 85 in the 1st week. Initial cerebrospinal fluid (CSF) was reactive with 34 white cells/mm3 (80% lymphocytes), normal glucose (more than 50% of blood glucose) and protein. Polymerase chain reaction (PCR) for Herpes, Enterovirus, Cytomegalovirus, Human herpes virus 6 was negative along with urine for toxicology. Blood, urine and CSF cultures were sterile. First MRI brain [] showed thickening of right temporal lobe gyrus, extending on to parietal lobe, with increased T2 signal within the cortex. There was associated restricted diffusion on diffusion-weighted imaging (DWI) []. She was treated for 2 weeks of third-generation antibiotics and acyclovir for probable encephalitis.\nPost-intensive care she remained confused, disorientated and had recurrent episodes of aggression and rage. She became mute and developed visual hallucinations. Sleep cycle was completely disrupted, and she was emotionally labile. Seizures were difficult to control initially but responded to a combination of Phenytoin and Levetiracitam. Repeat CSF examination was clear with normal biochemistry. PCR for Herpes and other viruses were negative.\nSerum VGKC-Abs were positive with titers of 1088 pM (normal < 100 pM). Further radiological investigations for possible underlying malignancy were negative. Treatment with high a dose oral prednisolone (60 mg) once daily for first 2 weeks followed by 4 weeks of weaning doses. The latency period from admission to immunotherapy was 3 weeks. There was slow but significant improvement in her symptoms following immunotherapy. The repeat serum VGKC-Abs titers after immunotherapy were negative, consistent with her clinical improvement. The neuropsychological evaluation before and after the immunotherapy suggested significant improvement in her cognition and behavior.\nRepeat MRI brain done after the treatment showed a reduction in the gyral thickening with improved grey-white matter differentiation and normal DWI. She received intense neurorehabilitation based at hospital and community following discharge. She has restarted in mainstream school after 6 months and has made near complete recovery.