Single-fiber electromyography during menstrual exacerbation and ovulatory suppression in MuSK antibody-positive myasthenia gravis.

We report a patient with muscle-specific tyrosine kinase (MuSK) antibody-positive myasthenia gravis who experienced worsening of myasthenic weakness associated with alterations in estrogen and progesterone levels during the administration of oral contraceptive therapy. Single-fiber electromyography was performed to document changes in neuromuscular transmission associated with the clinical exacerbation and subsequent resolution of the menstrual exacerbation and clinical improvement experienced with continuous monophasic oral contraceptive therapy. The potential long-term benefit of ovulatory suppression in MuSK antibody-positive myasthenia gravis is discussed.