Abstract

Natalizumab is used to treat highly-active relapsing-remitting multiple sclerosis. It is discontinued in certain clinical situations such as progressive multifocal leucoencephalopathy (PML) and pregnancy. Here we describe a case of cerebral and cervical cord immune reconstitution inflammatory syndrome (IRIS) causing florid CNS inflammation and severe disability in a pregnant patient after discontinuation of natalizumab. The patient was virtually symptom free prior to pregnancy but became bedbound, encephalopathic, hypertonic, and very ataxic after stopping natalizumab. She required 24 hour inpatient nursing care. After minimal response to steroids, clinical rescue was achieved by re-starting natalizumab during pregnancy and accepting a small risk to the foetus. The patient was delivered of a healthy baby girl some months later, and has made a virtually complete recovery. This difficult case highlights many of the dilemmas facing Neurologists as new, effective disease-modifying therapies come to clinic without the longitudinal data to guide decision-making.