Abstract
A patient with epilepsy on carbamazepine developed a rapidly progressive cerebellar syndrome. Serial MRI showed progressive posterior fossa T2/fluid attenuated inversion recovery hyperintensity with gadolinium enhancement. Standard cerebrospinal fluid (CSF) analysis was normal. Detection of John Cunningham virus DNA in the CSF confirmed progressive multifocal leukoencephalopathy (PML). The only evidence of immune disfunction was hypogammaglobulinaemia and longstanding lymphopenia. After cessation of carbamazepine, the lymphocyte count and immunoglobulin levels returned to normal and the PML resolved, with good clinical recovery. No specific treatments for PML were given. We hypothesise that PML in this case was due to carbamazepine-induced prolonged mild immunosuppression with reconstitution of the immune system after carbamazepine cessation, resulting in recovery from PML. Effects of anticonvulsants on immune function and infection risk may contribute to epilepsy-related morbidity and mortality. Further investigation is needed to determine the frequency of immune dysfunction and infections in patients treated with anticonvulsants such as carbamazepine and whether interventions could reduce infection risk.