title: [Progressive multifocal leukoencephalopathy associated to natalizumab: the importance of magnetic resonance imaging in its early diagnosis].
abstract: BACKGROUND
  Natalizumab is a drug used in multiple sclerosis (MS) and its main side effect is the development of progressive multifocal leukoencephalopathy (PML). Since this is potentially fatal or disabling, treatment must be stopped immediately if it is suspected, taking into account the possible later development of immune reconstitution syndrome or renewed exacerbation of MS.
  
  
  METHODS
  We report a case of initially asymptomatic PML within the context of treatment with natalizumab in a female patient with MS. High antibody titers to the John Cunningham virus (JCV) and over two years' treatment were established as risk factors. The polymerase chain reaction for the JCV in cerebrospinal fluid was negative in two determinations. The interval between the radiological diagnosis and the onset of the clinical features was two months. During the course of the disease, the patient developed immune reconstitution inflammatory syndrome and relapses, or renewed exacerbation, of her MS. She responded well after beginning treatment with fingolimod, once the PML had become stabilised.
  
  
  CONCLUSIONS
  This case indicates the importance of close clinico-radiological monitoring in patients with MS treated with natalizumab, especially when they present risk factors for the development of PML, as well as its potential incidence on survival and final functional status.
authors: Centre d'esclerosi multiple de Catalunya, Barcelona, Espana.
authors: Glòria
authors: G
authors: Martí
authors: Jordi
authors: J
authors: Río
authors: Àlex
authors: À
authors: Rovira
authors: Cristina
authors: C
authors: Auger
authors: Mar
authors: M
authors: Tintoré
authors: Jaume
authors: J
authors: Sastre-Garriga
authors: Anka
authors: A
authors: Vidal
authors: Joaquín
authors: J
authors: Castilló
authors: Xavier
authors: X
authors: Montalban
mesh_terms: D042241:Early Diagnosis; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000009:adverse effects* / Q000627:therapeutic use; D007968:Leukoencephalopathy, Progressive Multifocal / Q000139:chemically induced* / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000188:drug therapy; D000069442:Natalizumab / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D007155:Immunologic Factors; D000069442:Natalizumab