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June – Myasthenia Gravis Awareness Month

Generalized myasthenia gravis (MG) is a rare neuromuscular disorder that may be best known for causing drooping eyelids (called ptosis) and double vision. It affects the use of voluntary muscle groups and can create difficulty in swallowing, chewing and breathing; changes in speech; loss of facial expressions and weakness in the upper arms or legs because of an error in the transmission of nerve impulses to muscles. The thymus plays a major role in the development of the immune system and is associated with the development of MG. Occasionally MG can be associated with tumors in the thymus gland or thymic tissues. MG affects between 1 in 50,000 and 1 in 400,000 people, or between 36,000 and 60,000 Americans.

It’s most common in adults, but children and adolescents make up about 10 percent of all cases, with women showing a slightly higher incidence overall. Siblings and first-degree family members of affected patients have an increased risk for developing MG. Because therapies and diagnostic capabilities are improving, people are living longer with the disease; thus, the prevalence of MG is increasing.

ITxM delivers round-the-clock therapeutic hemapheresis services for a wide range of conditions, including MG in certain rare situations. For people with MG, therapeutic plasma exchange (TPE) is primarily reserved as a short-term, emergency treatment for patients with life threatening conditions like respiratory failure or for patients preparing for a more definitive long-term therapy such as thymectomy, (removal of the thymus). This acute treatment removes the pathogenic antibody in a patient’s plasma and replaces that plasma with albumin. Albumin is a sterile preparation manufactured with FDA oversight, derived from large pools of donated human plasma. Plasma donation is vital, and ultimately helps patients suffering from numerous disorders.

Many patients see the clinical effects of TPE within 24 hours of initiating therapy. However, the affect is relatively short-lived, lasting only a few weeks without a more definitive therapy.

Myasthenia Gravis is the best studied and most well understood autoimmune disease, and this body of knowledge about MG has helped improved routine therapy over the years. MG is primarily an antibody-mediated autoimmune disorder that affects neurological communication between nerves and muscles at the neuromuscular synapse. The pathogenesis of MG is a disturbance of neuromuscular transmission due to the development of autoantibodies, which bind to the acetylcholine receptor (AchR) itself, or other receptors involved in acetylcholine receptor clustering (Anti-MuSK, -LRP4, etc) at the neuromuscular junction. Approximately 85 percent of MG patients express AChR antibodies.

Pyridostigmine, an acetylcholinesterase inhibitor, is a first-line symptomatic therapy for MG, especially in patients with AChR antibodies. It is also used for oral long-term immunosuppression. Glucocorticoids and azathioprine are first line immunosuppressive therapies. Rituximab, an anti-CD20 monoclonal antibody, is an emerging treatment for MuSK MG patients who typically have poor responses to acetylcholinesterase inhibitors.

For more reading on myasthenia gravis, please refer to the following references:

1) Sanders DB, Wolfe GI, Benatar M, et al. International consensus guidance for management of myasthenia gravis: Executive summary. Neurology (2016) 87(4): 419-25.
2) Binks S, Vincent A, Palace J. Myasthenia gravis: a clinical-immunological update. J Neurol (2016) 263:826-834
3) Melzer N, Ruck T, Fuhr P, et al. Clinical features, pathogenesis, and treatment of myasthenia gravis: a supplement to the Guidelines of the German Neurological Society. J Neurol (2016) 263:1473-1494
4) Schwartz J, Padmanabhan A, Aqui N, et al. Guidelines on the Use of Therapeutic Apheresis in Clinical Practice—Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Seventh Special Issue. J Clin Apheresis (2016) 31:149–338.

 

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