Long-lasting treatment effect of rituximab in MuSK myasthenia.
OBJECTIVE
Rituximab has emerged as an efficacious option for drug-resistant myasthenia gravis (MG). However, reports published only describe the short-term follow-up of patients treated and little is known about their long-term clinical and immunologic evolution. Our objective was to report the clinical and immunologic long-term follow-up of 17 patients (6 MuSK+MG and 11 AChR+MG) and compare the response between AChR+MG and MuSK+MG patients.


METHODS
Myasthenia Gravis Foundation America postintervention status and changes in treatment and antibody titers were periodically determined. Lymphocyte subpopulations, total immunoglobulin, immunoglobulin G (IgG) anti-MuSK subclasses, and anti-tetanus toxoid IgG before and after treatment were also studied.


RESULTS
After a mean post-treatment period of 31 months, 10 of the AChR+MG patients improved but 6 of them needed reinfusions. In contrast, all MuSK+MG patients achieved a remission (4/6) or minimal manifestations (2/6) status and no reinfusions were needed. Consequently, in the MuSK+MG group, prednisone doses were significantly reduced and concomitant immunosuppressants could be withdrawn. Clinical improvement was associated with a significant decrease in the antibody titers only in the 6 MuSK+MG patients. At last follow-up MuSK antibodies were negative in 3 of these patients and showed a decrease of over 80% in the other 3.


CONCLUSIONS
In view of the long-lasting benefit observed in MuSK+MG patients, we recommend to use rituximab as an early therapeutic option in this group of patients with MG if they do not respond to prednisone.


METHODS
This study provides Class IV evidence that IV rituximab improves the clinical and immunologic status of patients with MuSK+MG.
Neuromuscular Disorders Unit, Neurology Department, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, Barcelona, Spain.
J
J
Díaz-Manera
E
E
Martínez-Hernández
L
L
Querol
R
R
Klooster
R
R
Rojas-García
X
X
Suárez-Calvet
J L
JL
Muñoz-Blanco
C
C
Mazia
K R
KR
Straasheijm
E
E
Gallardo
C
C
Juárez
J J
JJ
Verschuuren
I
I
Illa
D000328:Adult; D058846:Antibodies, Monoclonal, Murine-Derived / Q000627:therapeutic use*; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000627:therapeutic use; D008137:Longitudinal Studies; D008297:Male; D009157:Myasthenia Gravis / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy*; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology*; D000069283:Rituximab; D016896:Treatment Outcome
D058846:Antibodies, Monoclonal, Murine-Derived; D001323:Autoantibodies; D007155:Immunologic Factors; D011950:Receptors, Cholinergic; D000069283:Rituximab; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases