Development of novel drugs provides new hope to patients with serious diseases. However, new compounds might also be associated with poorly known adverse events.
The same applies to the field of multiple sclerosis where, in addition to the presently well-established standard treatment with beta-interferons and glatiramer acetate, new potent drugs have recently emerged. Natalizumab and fingolimod are the two already registered for use in the Czech Republic.
This case report is concerned with the first occurrence of progressive multifocal leukoencephalopathy in a female patient treated with natalizumab in the Czech Republic. The importance of early diagnosis and treatment is emphasised as the only measures currently available with a potential to positively influence a patient’s outcome.