Prolonged improvement after rituximab: two cases of resistant muscle-specific receptor tyrosine kinase + myasthenia gravis.

Forty percent to 50% of acetylcholine receptor antibody-seronegative patients with myasthenia gravis have muscle-specific receptor tyrosine kinase antibodies. Many muscle-specific receptor tyrosine kinase + myasthenia gravis patients remain refractory with conventional therapies. Rituximab is an anti-CD20 monoclonal antibody used in refractory B-cell disorders. Currently there is no standard dosing schedule for rituximab. We present two muscle-specific receptor tyrosine kinase + myasthenia gravis patients clinically refractory to conventional therapy who, after a single course of rituximab, became asymptomatic and discontinued all medication.