Razi Journal of Medical Sciences

Background: Myasthenia gravis is an autoimmune disorder mainly caused by antibodies to the muscle acetylcholine receptors (AChR-Ab) at the neuromuscular junction. Loss of these receptors leads to a defect in neuromuscular transmission with muscle weakness and fatigue. This antibody is not detected in all the patients and electrophysiologic study is necessary in some patients as a diagnostic tool. The serologic and electrophysiologic tests in Myasthenia gravis are evaluated in this study.

Methods: One hundred twelve patients entered in a cross-sectional study. Serum AChR-Ab was measured and Repetitive nerve stimulation (RNS) was done. The frequency of positive AChR-Ab and abnormal RNS and the relationship between them were determined.  

Results: Thirty (26.8%) patients were males and 82 (73.2%) were females. Mean of age was 37.6±15.4 years. AChR-Ab was positive in 71 (63.4%) and negative in 41 (36.6%). RNS was done in 101 patients and was abnormal in 74 (73.3%) and normal in 27 (26.7%) patients. Ratio of abnormal RNS was 84.4% and 53.7% in seropositive and seronegative patients, respectively (p=0.001). 

Conclusion: There is significant relationship between serologic and electrophysiological findings in Myasthenia gravis. Combining electrophysiological and serological tests could increase the accuracy of Myasthenia gravis diagnosis.