Cerebral protothecosis mimicking high-grade glioma.

is a common, indolent alga that seldom causes central nervous system infections in humans. We report the first UK case of cerebral protothecosis in an immunocompetent 56-year-old woman who presented with a 5-month history of intermittent fatigue followed by a 2-week history of symptoms, including right arm and leg weakness, a loss of fine motor coordination, worsening gait, right facial tingling, diplopia and a metallic oral taste. MRI scans revealed a multifocal abnormality suggestive of high-grade glioma. Given the clinical presentation, absence of immunodeficiency and characteristic MRI features, a diagnosis of high-grade glioma was deemed most likely by the multidisciplinary team. Surgical biopsy provided material for histopathological and microbiological diagnosis. She underwent a 2-year course of antimicrobials with surveillance MRI scans. The patient made a good functional recovery but still retains mild neurological sequelae.