James F. Howard, Jr, MD, professor of neurology at the University of North Carolina at Chapel Hill, explains the antibody subtypes associated with this rare neuromuscular disease.
Myasthenia gravis treatment needs to be customized to the needs of individual patients, according to James F. Howard, Jr, MD, professor of neurology at the University of North Carolina at Chapel Hill, former chief of the Neuromuscular Disorders Division, and former James F. Howard Distinguished Professor of Neuromuscular Disease. In this interview, he explained the antibody subtypes associated with this rare neuromuscular disease.
What are some of the key differences in myasthenia gravis, depending on the antibody subtype?
So, acetylcholine receptor antibody–positive is the largest group we see, representing somewhere around 85%. And the numbers change as our technology improves and we can identify newer antibodies. MuSK [muscle specific kinase] myasthenia represents 8% to 9%. LRP4 [lipoprotein-related protein 4] is down around 1% or less. Then there's a group of patients for which we have not identified an antibody as yet. There is some circulating factor, I believe, as they respond to things like plasma exchange or antibody clearance drugs, etc. It’s important to recognize which antibody one has, because our therapeutic options change. For instance, MuSK myasthenia does not respond to surgical thymectomy. [These patients are] very often, in more than 70%, hypersensitive or allergic or intolerant of a class of drugs called cholinesterase inhibitors, most commonly pyridostigmine, or Mestinon.
And so it's important that these antibody subtypes be identified in order that we can plan the appropriate therapeutic intervention. The treatment of myasthenia is not a cookbook. It has to be tailored to the specific individual in the US based on a whole host of factors, not the least of which is the financial resources that they have.
But their comorbidities, the pattern of muscle weakness, the rapidity with which that weakness came on—so if someone has smoldering weakness in arms and legs, it will be treated totally different than if one comes in saying I can't chew, swallow, or I'm having respiratory difficulties—and knowing which antibody subtype often helps in determining what will be our overall game plan.