Case Report: Re-investigating recurrent Refractory Status Epilepticus revealed POLG-Related Mitochondrial Disease

<ns5:p> We present a case of a 21-year-old adult female with a history of chronic focal epilepsy and a learning disability presumed to be secondary to a traumatic brain injury due to shaken baby syndrome. She had a previous admission to a district general hospital with refractory status epilepticus precipitated by an infection, which was complicated by an apparent thalamic infarct. On this occasion she presented with super-refractory status epilepticus precipitated by a chest infection. Seizure control required use of multiple anaesthetic agents combined with six anti-epileptic drugs. Multiple refractory status presentations precipitated by infection, imaging and EEG findings raised the suspicion of mitochondrial disease. Urgent genetic testing was undertaken which revealed a homozygous Polymerase g ( <ns5:italic>POLG</ns5:italic> ) pathogenic variant, not known previously, consistent with a diagnosis of a <ns5:italic>POLG</ns5:italic> -related mitochondrial disorder. Antiepileptic therapy was optimized while avoiding hepatotoxic agents, resulting in substantially improved seizure control. This case highlights the importance of considering <ns5:italic>POLG</ns5:italic> variants as a cause of chronic focal-onset epilepsy, with refractory and super-refractory epilepsy presentations, even when there are apparent alternative explanations for seizures. Characteristic EEG and imaging findings involving posterior brain regions should further raise suspicion of <ns5:italic>POLG</ns5:italic> -related mitochondrial disease. This case also underlines the utility of rapid genetic testing in unwell adults, not only for diagnosis, but to guide anti-epileptic therapy and prognosis in patients with refractory and super-refractory status epilepticus. </ns5:p>