LAUSR

© BMJ Publishing Group Limited 2022. No commercial reuse. See rights and permissions. Published by BMJ. DESCRIPTION A previously well immunocompetent man in his 60s presented with a 3month history of subacute altered mental state and seizures. On clinical examination, he was confused but had no focal neurological deficits. Cerebrospinal fluid (CSF) examination showed minimal cells with an elevated protein of 1.1 g/dL. EpsteinBarr virus (EBV) PCR was positive in the CSF but other bacterial, viral serology and CSF cytology were negative. An extensive panel of autoimmune and paraneoplastic encephalitis antibodies tested negative. MRI brain showed multiple brain lesions with an incomplete (openring) pattern of enhancement (figure 1). These were hyperintense on T2weighted images with no restricted diffusion. The patient was treated for ‘tumefactive’ inflammatorydemyelinating pathology with corticosteroids and plasma exchange but there was no improvement in his symptoms. He developed haemophagocytic lymphohistiocytosis and further increase in size of the brain lesions. A brain biopsy revealed extranodal natural killer/Tcell lymphoma (NKTL). Blood EBV titres were markedly elevated at up to 310 000 IU/mL and EBVencoded RNA was demonstrated in the brain tissue. Unfortunately, he did not respond to immunotherapy treatment with nivolumab and died about 6 weeks after presentation. As evidenced in this case, we caution against overinterpreting the specificity of the ‘openring’ enhancement pattern, with no restricted diffusion, as a sign of inflammatory aetiology. 2 The lack of response to immunosuppressive treatment and EBV positivity were unusual for an inflammatory disease process and prompted histological confirmation with a brain biopsy. NKTL is a highly aggressive and rare form of nonHodgkin’s lymphoma associated with EBV infection. It occurs more commonly in the Asian population and typically affects the upper aerodigestive tract such as the nasopharynx and sinuses. Central nervous system involvement is extremely rare and often heralds a poor prognosis.