Myasthenia gravis with antibodies to MuSK: an update

Myasthenia graviswith antibodies to themuscle-specific tyrosine kinase(MuSK+ MG)is a rare diseasewith distinctive pathogenic mechanisms and clinical features. An acute onset and predominant bulbar muscle weakness are very commonand highly suggestive of the disease.On the other hand, amore indolent course, atypical ocular presentation, and signs of cholinergic hyperactivity may complicate the diagnosis. ThoughMuSK+ MGis still a severe disease, over the years we have observed a steady reduction in the rate of respiratory crisis and a significant improvement in the clinical outcome, both likely related to earlier diagnosis and timely treatment. Despite the improved management, MuSK+ MG patients tend to remain dependent on long-term immunosuppressive treatment and may develop permanent disabling weakness. In uncontrolled studies, B cell depletion with rituximab proved effective in most patientswith refractory disease, inducing prolonged clinical responses associatedwith a sustained reduction of serum antibody levels. Promising results fromexperimental studies and case reports suggest that both 3,4-diaminopyridine and albuterol may be effective as symptomatic agents.