MuSK-antibody-positive myasthenia gravis in a South Asian population.
BACKGROUND
MuSK-antibody-positive myasthenia gravis (MuSK-MG) is diagnosed in 0-40% of cases with generalized seronegative MG in different populations. The presence of anti-MuSK antibodies defines a distinct clinico-immuno-pathological subtype of MG. We analysed for the first time the serology and clinical characteristics of MuSK-MG in a South Asian population.


METHODS
113 patients with MG attending Neurology Units in three state hospitals in the district of Colombo, Sri Lanka were studied. AChR antibodies were tested in all patients whilst MuSK antibodies were tested in patients seronegative for AChR antibodies. Sera from patients with other neurological diseases (OND) concurrently attending the same hospitals were obtained as controls.


RESULTS
Four of 19 AChRAb-negative generalised MG patients (21%) were positive for MuSKAbs. Two were women and in 3, disease onset was before the age of 30 years. Although 3 of 4 had ocular-bulbar involvement at presentation, none had facial or bulbar muscle wasting. Two of the 4 patients (50%) had developed myasthenic crisis and had required ventilation. A good treatment outcome appears to be related to early commencement of immunosuppressive medication. None of the patients with ocular MG or OND were positive for either AChR or MuSK antibodies.


CONCLUSIONS
MuSK-MG is seen in about a fifth of generalised seronegative MG patients in Sri Lanka. The clinical characteristics are consistent with features described in Caucasian MuSK-MG patients.
Chang
Thashi
T
Department of Clinical Medicine, University of Colombo, Sri Lanka. thashichang@gmail.com
Gunaratne
Padma
P
Gamage
Ranjanie
R
Riffsy
M T M
MT
Vincent
Angela
A
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000918:Antibody Specificity; D044466:Asian People / Q000706:statistics & numerical data; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000145:classification / Q000453:epidemiology / Q000208:ethnology / Q000276:immunology*; D009422:Nervous System Diseases / Q000276:immunology; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology*; D013188:Sri Lanka / Q000453:epidemiology
D001323:Autoantibodies; D001324:Autoantigens; D011950:Receptors, Cholinergic; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases