MuSK-antibody positive myasthenia gravis: clinical and electrodiagnostic patterns.
OBJECTIVE
To examine the clinical manifestations and patterns of electromyographic abnormalities in MuSK-Ab positive myasthenia gravis.


METHODS
The clinical evaluations and electrodiagnostic testing results of 20 MuSK-Ab positive myasthenia gravis patients were retrospectively reviewed and compared with matched AChR-Ab positive (N = 72) and MuSK-Ab negative/AChR-Ab negative (N = 24) patients.


RESULTS
MuSK-Ab positive patients were younger and more frequently female and African-American, and compared to the AChR-Ab positive patients, were more likely to present with respiratory symptoms or neck extension weakness. MuSK-Ab positive patients were less likely to have abnormal jitter in a limb muscle: only 59% had abnormal jitter in the extensor digitorum communis muscle, compared to 80% of the AChR-Ab negative/MuSK-negative patients and 91% of the AChR-Ab positive patients.


CONCLUSIONS
Our MuSK-Ab positive patients not only differ demographically from our MuSK-Ab negative cohort, but they also appear to have a more limited distribution of SFEMG abnormalities.


CONCLUSIONS
The possibility that electrophysiologic abnormalities may not be widely distributed should be considered during electrodiagnostic evaluation of suspected MuSK-Ab positive MG and in selecting muscles for molecular, morphologic, or microphysiologic studies in this condition.
Stickler
D E
DE
Division of Neurology, Duke University Medical Center, Durham, NC 27710, USA.
Massey
J M
JM
Sanders
D B
DB
D000328:Adult; D001741:Black or African American; D000368:Aged; D001323:Autoantibodies / Q000032:analysis*; D015331:Cohort Studies; D004558:Electric Stimulation; D004568:Electrodiagnosis; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009157:Myasthenia Gravis / Q000175:diagnosis / Q000276:immunology* / Q000503:physiopathology*; D009460:Neurologic Examination; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology* / Q000378:metabolism; D012189:Retrospective Studies; D044465:White People
D001323:Autoantibodies; D011950:Receptors, Cholinergic; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases