Neurol. praxi. 2021;22(2):121-127 | DOI: 10.36290/neu.2020.109

MuSK antibody positive myasthenia gravis - our experience

doc. MUDr. Peter Špalek, PhD.¹, MUDr. Ivan Martinka, PhD.¹, MUDr. Štefan Kečkeš²

¹ Centrum pre neuromuskulárne ochorenia, Národné expertízne centrum pre zriedkavé neuromuskulárne ochorenia, Neurologická klinika SZU a UNB, Nemocnica Ružinov, Bratislava

² Oddelenie hematológie a transfuziológie OÚSA a Vysoká škola zdravotníctva a sociálnej práce sv. Alžbety, Bratislava

Myasthenia gravis (MG) is a rare autoimmune disease of the neuromuscular junction manifested by pathological fatigue and muscle weakness of fluctuating intensity. MG is a heterogeneous disease. The MG subtypes are very rare, differ in their etiopathogenetic mechanism, age at onset and responsiveness to treatment. Anti-MuSK positive MG is a rare MG subtype with 2-4 % ratio of all MG forms. The etiopathogenetic basis of anti-MuSK positive MG is the production of antibodies against muscle-specific kinase (MuSK). As a result of anti-MuSK autobodies production the neuromuscular junction (NMJ) regeneration is impaired, acetylcholine receptor (AChR) density is reduced, their distribution at the NMJ postsynaptic membrane is altered and leading to an impairment of neuromuscular transmission. Anti-MuSK MG develops mainly at younger age < 50 years, affects more often females than males (3 : 1) and usually manifests with acute generalized myasthenic symptoms. Due to generalized symptoms and relatively frequent fulminant onset, intensive immunosuppressive therapy, usually including interventional immunotherapy (plasmapheresis and/or IVIG), are immediately indicated. Anti-MuSK positive MG has an extrathymic immunopathogenesis, thymus is involved and thymectomy is not indicated. The prognosis of anti-MuSK MG patients is relatively good if the disease is diagnosed early and intensive immunosuppressive treatment is indicated at the beginning of the disease. A small proportion of patients do not respond well to treatment, the drug of choice in refractory cases is rituximab. We also report our experiences with a cohort of 39 anti-MuSK MG patients in Slovak Republic.

Keywords: anti-MuSK positive MG, immunopathogenesis, generalized myasthenic manifestation, diagnosis, treatment.

Received: October 29, 2020; Revised: November 2, 2020; Accepted: November 2, 2020; Prepublished online: November 2, 2020; Published: April 30, 2021  Show citation