Myasthenia Gravis

Myastheni Gravis
Myasthenia Gravis (MG) is an autoimmune disorder characterized by muscle weakness that ranges from mild weakness of specific muscle groups to severe weakness of multiple muscle groups. MG affects approximately 20 per 100,0001 patients and arises from antibody-mediated synaptic dysfunction of the transmission of nerve impulses to muscle fibers at the neuromuscular junction. This disruption involves either acetylcholine receptors (AChR) or muscle-specific kinase receptors (MuSK) that ultimately inhibit muscle contraction. Onset of symptoms is generally gradual, but can sometimes be acute following viral infection or pregnancy.

 

Symptoms of Myasthenia Gravis

What are the symptoms of MG?1,2

  • Weakness and fatigue of skeletal muscles, ranging from mild weakness to severe weakness of multiple muscle groups. 90% have ptosis or diplopia with pupillary involvement.
  • MuSK antibody-positive patients experience more pronounced bulbar weakness and may have tongue and facial atrophy.

 

AChR Positive Patients

  • Limb weakness, ptosis, diplopia, dysarthria, dysphagia

 

MuSK Positive Patients

  • Bulbar weakness is predominant, and can include ptosis, diplopia, dysarthria, facial weakness, difficulty chewing or swallowing; other signs and symptoms may vary.

 

1Haven TR, Astill ME, Pasi BM. An Algorithm for Acetylcholine Receptor Antibody Testing in Patients with Suspected Myasthenia Gravis. Clinical Chemistry. 2010; 56(6): 1028-1029.