A comparison of long-term post-thymectomy outcome of anti-AChR-positive, anti-AChR-negative and anti-MuSK-positive patients with non-thymomatous myasthenia gravis.
OBJECTIVE
A single-centre, non-randomized, non-controlled study was designed to compare the long-term post-thymectomy clinical outcome in anti-AChR-positive, anti-AChR-negative and anti-MuSK-positive patients with non-thymomatous myasthenia gravis (MG).


METHODS
A total of 331 consecutive patients with seropositive MG, 55 with seronegative MG and 10 with anti-MuSK-positive MG underwent extended transsternal thymectomy (T-3b according to Myasthenia Gravis Foundation of America). The primary endpoint was to assess differences in the rate of complete stable remission (CSR) in patients with and without anti-AChR and anti-MuSK antibodies.


RESULTS
The mean follow-up was 218.3 (SD 128.1) months in the seropositive MG group, 149.8 (SD 131.1) in the seronegative group and 169.9 (SD 116) in the anti-MuSK-positive group. In the seropositive MG group, the probability of obtaining CSR at 5 years post-thymectomy was 51.1% for the seropositive group compared with 40 for the seronegative group (p = 0.05) and 20 for the anti-MuSK-positive group (p = 0.03). Differences between the seronegative and anti-MuSK-positive groups were not observed. The estimated median follow-up to obtain a CSR was 17.8 months (95% confidence interval [CI] 15.7 - 19.8 months) in seropositive MG patients, 22.1 (95% CI 16.7 - 27.4 months) in seronegative MG patients and 20.6 (95% CI 13.3 - 27.9 months) in anti-MuSK-positive MG patients (long-rank test, p = 0.07).


CONCLUSIONS
Long-term post- thymectomy clinical outcome was better in patients with conventional anti-AChR antibodies than in those with seronegative disease. In seronegative anti-MuSK-positive MG, thymectomy seems to be less effective than in anti-MuSK-negative MG but this study cannot answer the question of whether thymectomy should be undertaken in anti-MuSK-positive patients.
Ponseti
José M
JM
Unit of Myasthenia Gravis, Autonomous University of Barcelona, Hospital General Universitari Vall d'Hebron, Department of Surgery, Barcelona, Spain. jmponseti@vhebron.net
Caritg
Norma
N
Gamez
Josep
J
López-Cano
Manuel
M
Vilallonga
Ramón
R
Armengol
Manuel
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000276:immunology / Q000601:surgery*; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology*; D012189:Retrospective Studies; D013934:Thymectomy
D011950:Receptors, Cholinergic; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases