A subtype of acetylcholine receptor (AChR) antibody that blocks the receptor may provide useful information about the severity of myasthenia gravis (MG) and the risk of ocular disease progressing to generalized MG, according to a longitudinal study published recently in Neurological Sciences.
AChR antibodies have three subtypes: binding, modulating and blocking. Blood tests that look for AChR-binding antibodies are routinely used to diagnose MG. The study’s findings suggest that measuring AChR-blocking antibodies as well could might help clinicians better understand disease progression.
“Although binding antibodies remain central to MG diagnosis, blocking antibodies show a more consistent association with disease severity,” the study’s investigators said. “Their possible role in identifying patients at risk of generalization further underscores their clinical relevance.”
Read more about MG prognosis here
Researchers followed 47 people with AChR-positive MG for a mean of 2.8 years, collecting 121 antibody measurements. Blocking antibodies were detected in 38 patients (80.9%).
Generalized MG was present in 42 patients (89.4%), while five had disease that remained limited to the eyes. Blocking antibodies were detected in 90.5% of patients with generalized MG, whereas none of those with persistently ocular disease tested positive.
Sign up here to get the latest news, perspectives and information about myasthenia gravis sent directly to your inbox. Registration is free and only takes a minute.
The results were particularly notable among the 13 patients whose MG initially affected only the eyes. Eight progressed to generalized disease during follow-up — and all eight had detectable blocking antibodies. None of the five patients whose disease remained ocular had blocking antibodies. Blocking antibody levels also were significantly higher in patients with generalized MG than in those with ocular disease.
The researchers also examined whether antibody levels were associated with MG severity over time using Myasthenia Gravis Foundation of America severity scores. They found that blocking antibodies showed a significant association with greater severity. This relationship remained significant after accounting for time since diagnosis, age and sex and in additional analyses that considered thymoma and treatment status.
By comparison, AChR-binding antibodies were not significantly associated with Myasthenia Gravis Foundation of America severity scores. Additional statistical analyses produced similar results, strengthening the finding that blocking antibody activity was more closely related to disease severity than binding antibody levels in this group.
For patients, the findings could eventually mean more precise information about the likelihood that ocular MG will become generalized. However, the study does not establish that changes in blocking antibody levels within an individual necessarily predict changes in symptoms. The study also included only AChR-binding antibody-positive patients and mostly people with generalized MG. Larger prospective studies are needed before blocking antibody testing can be routinely used to predict disease progression.
