Antibodies & Myasthenia Gravis: Insights from Dr. Henry Kaminski’s May 2025 Webinar

In May 2025, the Myasthenia Gravis Association hosted an expert webinar featuring Dr. Henry Kaminski from George Washington University. The presentation, titled “Antibodies and MG,” provided critical information regarding antibodies and antibody testing in Myasthenia Gravis (MG), highlighting the importance of antibody profiling in diagnosis, treatment, and clinical diagnosis in combination of antibody identification. This blog post summarizes Dr. Kaminski’s key points, elaborates on antibody test limitations, and discusses clinical relevance.

Antibody Subtypes in Myasthenia Gravis

• Acetylcholine Receptor (AChR) Antibodies

  • AChR antibodies are the most common MG antibodies, detected in approximately 85% of individuals with generalized MG but only around 50% of those with ocular MG. These autoantibodies target the nicotinic acetylcholine receptor at the neuromuscular junction, disrupting signal transmission and causing muscle weakness.

  
  

• Muscle-Specific Kinase (MuSK) Antibodies

  • MuSK antibodies are present in approximately 5-10% of individuals with MG, typically those who test negative for AChR antibodies. MuSK-positive MG often manifests with prominent bulbar symptoms and can respond better to B-cell–targeted therapies like rituximab.

  
  

• Emerging Antibodies: LRP4, Agrin, and Others

  • Additional antibodies such as low-density lipoprotein receptor-related protein 4 (LRP4) and agrin have been identified in subsets of “seronegative” individuals with MG (those negative for AChR and MuSK). Although less common, their detection can significantly reduce misdiagnosis and guide treatment decisions.

Clinical Relevance by Antibody Type

• AChR-positive MG: Responsive to standard therapies including acetylcholinesterase inhibitors, corticosteroids, IVIG, plasma exchange, and newer complement inhibitors such as eculizumab.

• MuSK-positive MG: Often resistant to acetylcholinesterase inhibitors but responsive to rituximab and immunosuppressants targeting B cells.

• LRP4-positive and Seronegative MG: Require individualized clinical evaluation, with some individuals benefiting from clinical trial participation or novel therapies.

  
  

Avoiding Misdiagnosis & Understanding Test Limitations

No antibody test is 100% sensitive or specific; thus, a comprehensive clinical evaluation remains essential.

Limitations of MG Antibody Tests

Antibody	Sensitivity & Specificity	Limitations	Cross-Reactivity
AChR	~85% generalized MG, ~50% ocular MG	False negatives in early/mild disease; low sensitivity in ocular MG	Rare low-level positives in systemic autoimmune diseases
MuSK	~5-10% MG cases, especially AChR-negative	Possible false negatives; symptoms can overlap with other neuromuscular disorders	Generally specific to MG; rare reports outside MG
LRP4	Detected in ~2-5% of seronegative MG	Testing not widely standardized; positivity in some healthy individuals	Positivity reported in ALS and other neurological diseases
Agrin	Emerging antibody; small subset	Experimental testing; clinical significance under research	No strong evidence for cross-reactivity; research ongoing

When antibody tests are negative yet clinical suspicion remains high, repeat testing broader antibody panels, electrophysiological testing (single-fiber EMG, repetitive nerve stimulation), and referral to MG specialists are recommended to improve diagnostic accuracy.

What You Can Do

• Request a comprehensive antibody panel: including AChR, MuSK, LRP4, and agrin antibodies.

• Consult an MG specialist: for accurate diagnosis and personalized care.

• Seek reevaluation: if symptoms persist despite negative antibody tests.

• Understand that diagnosis is clinical: antibody testing supplements but does not replace clinical judgment.

• Monitor symptoms: and adjust treatments accordingly.

• Don't assume all your symptoms are from your MG. Dr. Kaminski emphasized the critical importance of avoiding misdiagnosis, as multiple neuromuscular and autoimmune disorders, and other more common conditions can coexist together.

  
  

Conclusion

Dr. Kaminski’s webinar underscores the evolving landscape of MG antibody testing and its essential role in accurate diagnosis and tailored treatment. Awareness of antibody test limitations and potential for coexisting conditions highlights the need for comprehensive clinical and laboratory evaluation. By integrating antibody profiles into clinical practice, providers can improve patient outcomes through personalized therapies, and individuals can better understand their condition and treatment options.

Watch the full webinar, including an extensive Q&A, on our YouTube channel or below.