A 35-year-old woman presents with relapsing-remitting MS confirmed on McDonald 2017 criteria. She is started on natalizumab. The risk of PML (progressive multifocal leukoencephalopathy) is determined by:
- A CD4 count below 200 cells/μL
- B MRI lesion burden and prior interferon-beta exposure
- C Duration of natalizumab therapy and prior immunosuppressant use and anti-JC virus antibody index ✓
- D Presence of HLA-DRB1*15:01 allele
Correct answer: C. Duration of natalizumab therapy and prior immunosuppressant use and anti-JC virus antibody index
Explanation
PML risk with natalizumab (anti-α4-integrin monoclonal antibody) is stratified by three factors: anti-JC virus antibody seropositivity (and index >0.9 confers highest risk), duration of natalizumab therapy (>24 months significantly increases risk), and prior immunosuppressant use. CD4 monitoring is relevant for HIV-associated PML, not natalizumab PML. HLA-DRB1*15:01 is associated with MS susceptibility, not PML.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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