American Board of Internal Medicine (ABIM) Certification Practice Exam 2025 - Free ABIM Practice Questions and Study Guide

The severe complication associated with the use of natalizumab for multiple sclerosis is progressive multifocal leukoencephalopathy (PML). This is a rare but serious viral infection of the brain caused by the John Cunningham virus (JCV), which can lead to severe neurological impairment and is often fatal.

Natalizumab is a monoclonal antibody that works by inhibiting the migration of immune cells into the central nervous system, thereby reducing inflammation and damage that occurs in multiple sclerosis. However, this immunosuppressive effect can increase the risk of opportunistic infections, particularly in individuals who are JCV seropositive.

Patients receiving natalizumab are at an increased risk for PML, especially after prolonged exposure to the drug. Regular monitoring for symptoms of PML during treatment is essential. The awareness of this complication plays a critical role in the patient management plan for individuals on natalizumab therapy.