This is a really important question to bring up with your neurologist, because the answer isn't a simple yes or no.
Dimethyl fumarate (sold as Tecfidera or Bafiertam) has been linked to a small number of PML cases — a serious brain infection that can occur when the JC virus becomes active in people with a weakened immune Show Full Answer
This is a really important question to bring up with your neurologist, because the answer isn't a simple yes or no.
Dimethyl fumarate (sold as Tecfidera or Bafiertam) has been linked to a small number of PML cases — a serious brain infection that can occur when the JC virus becomes active in people with a weakened immune system. Since dimethyl fumarate can lower lymphocyte (white blood cell) counts, it may increase that risk. Here's what's generally recommended if you've tested positive for JC virus exposure:
- Tell your neurologist right away so they can factor this into your treatment plan
- Regular blood monitoring is typically required while on dimethyl fumarate to watch lymphocyte levels
- Weigh the risks and benefits with your doctor — many people do continue treatment with careful monitoring
- Watch for any new or unusual symptoms, such as changes in vision, speech, muscle weakness, or cognition, and report them promptly
The good news is that there are many MS treatment options available today, so if dimethyl fumarate isn't the right fit, alternatives can be explored with your care team.
AI-generated responses are not a substitute for medical advice. These services are not intended to
diagnose, treat, or cure any condition or disease. Always ask your doctor about specific health concerns.
JC Virus, PML, and Multiple Sclerosis
October 16
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