Incidence of Abnormal Acetylcholine Receptor, Striatal Muscle, and MUSK Antibodies in Voice Patients with Myasthenia Gravis of the Larynx

Laryngeal myasthenia gravis (LMG) is an autoimmune disorder of the neuromuscular junction whose clinical presentation involves fluctuating and fatigable laryngeal muscle weakness due to antibody-mediated disruption of acetylcholine transmission at the post-synaptic cleft. LMG is a subtype of myasthenia gravis and is thought to be similar to a well-characterized variant of myasthenia gravis, ocular myasthenia gravis. These conditions are similar in that the disease manifestation is focal and that a high percentage of patients are seronegative. It has been postulated that in seronegative patients, antibodies to neuromuscular junction components exist but are localized to the neuromuscular junction and thus not present in appreciable amounts in serum. Furthermore, the clinical presentation of LMG patients is heterogenous; dysphonia and aphonia are common, though some cases present with shortness of breath and stridor, posing a threat to airway patency when the posterior cricoarytenoid muscle in involved. Patients with myasthenia gravis have been noted at the senior author’s practice that present with dysphonia and not with airway compromise. It is thought that patients presenting with this rare variant appear to have heterogeneous serologic results with a low proportion testing positive for anti-acetylcholine receptor or anti-MUSK antibody. Therefore, better understanding of the incidence of abnormal acetylcholine receptor, MuSK, and striated muscle antibodies is necessary to advance diagnostic recognition and treatment of laryngeal myasthenia. Characterization of the incidence of antibodies to the components of the neuromuscular junction has not been reported comprehensively in voice patients in many of whom unimpaired phonation is critical for vocational pursuits. The characterization of these patients will also allow for the authors to further describe the subgroup characteristics of voice patients who present with LMG.