The features of myasthenia gravis with autoantibodies to MuSK.
OBJECTIVE
To determine if myasthenia gravis (MG) with antibodies to MuSK is a distinct subgroup of seronegative MG.


METHODS
We assayed antibodies to muscle specific tyrosine kinase (MuSK) in 55 MG patients who had no antibodies to acetylcholine receptors and looked for the specific phenotype, comparing clinical features of anti-MuSK positive and anti-MuSK negative MG patients.


RESULTS
MG with anti-MuSK antibodies was characterised by a striking prevalence of female patients (15 women, two men). Age at onset ranged from 22 to 52 years, with 70.6% of patients presenting at < 40 years of age. The majority of patients (82.4%) had prevalent involvement of facial and bulbar muscles. One third of them did not respond well to anticholinesterase drugs. Steroid immunosuppression was effective in eight patients (44.4%). Nine patients underwent thymectomy; six of these had no thymus pathology, while three had a hyperplastic thymus. At the end of the observation period, six (35.3%) patients were in remission, five (29.4%) improved, four (23.6%) did not change, and two (11.7%) had died.


CONCLUSIONS
MG patients with antibodies to MuSK have characteristic clinical features that are different from features of the remaining seronegative MG patients. This emphasises the predictive value of anti-MuSK antibody analysis in seronegative MG patients.
Lavrnic
D
D
The Institute of Neurology, Clinical Centre of Serbia, 11000 Belgrade, 6 Dr Subotica Street, Serbia and Montenegro. joltruth@sezampro.yu
Losen
M
M
Vujic
A
A
De Baets
M
M
Hajdukovic
L J
LJ
Stojanovic
V
V
Trikic
R
R
Djukic
P
P
Apostolski
S
S
D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D001323:Autoantibodies / Q000276:immunology*; D004576:Electromyography; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000276:immunology / Q000503:physiopathology; D009157:Myasthenia Gravis / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology; D011237:Predictive Value of Tests; D015995:Prevalence; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology*; D017678:Sex Distribution; D013934:Thymectomy / Q000706:statistics & numerical data; D013950:Thymus Gland / Q000473:pathology / Q000601:surgery
D001323:Autoantibodies; D011950:Receptors, Cholinergic; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases