Therapeutic Plasma Exchange for Myasthenia GravisClifford Blieden, MD

Houston Methodist HospitalDepartment of Pathology and Genomic Medicine, Division of Transfusion Medicine

Who Are We?• Physicians with residency training in Clinical Pathology with or

without Anatomic Pathology• Fellowship trained in Transfusion Medicine• WE TAKE CALL!!!!

Myasthenia Gravis• Neuromuscular disorder caused by circulating autoantibodies

to the acetylcholine receptors in the post synaptic neuromuscular junction

• Associated with a variety of other autoimmune diseases such as Hashimotos thyroiditis, type I diabetes, lupus

Common Modalities for Diagnosing Myasthenia Gravis• Serologic testing• Acetylcholine receptor antibodies• Muscle specific (MuSK) receptor antibodies

• 50% of seronegative MG patients may have antibodies to MuSK

• Muscle electromyography• Edrophonium (cholinesterase inhibitors) test• Muscle biopsy • IgG deposition at neuromuscular junction by

immunofluorescence

Current Treatment Options• Medications:• Increase acetylcholine (cholinesterase inhibitors; neostigmine,

pyrostigmine)• Decrease immune response (corticosteroids)

• Plasma exchange to remove antibodies• Thymectomy• Thymoma and MG are frequently associated

Plasmapharesis• Word is derived from “plasma” and Greek word “aphaeresis”

(take away)• Blood is removed from the body and separated into separate

components (plasma and red cell component)• Continuous process requiring an afferent and efferent site of

blood supply.

Why Plasma Exchange?• Antibodies reside in the plasma component of the blood• Removal of these antibodies temporarily decreases symptoms

of myasthenia gravis• Scheduled plasma exchange regimen useful in patients with

disease not helped by medications

TPE and Myasthenia Gravis• TPE is used to remove antibodies present in the plasma

component• May be applied in multiple settings (outpatient, inpatient,

perioperative) • Regarded as a category I indication (ASFA guidelines)• Category I = disorders for which apheresis is accepted as first

line therapy, either alone or in conjunction with other treatment modalities

• Patients MAY experience improvement of symptoms within 24 hours

Common side effects of plasma exchange• Paresthesia• Hypotension • Urticaria• Nausea• Abdominal cramps

Hypocalcemia• Common occurrence with plasma exchange due to citrate, an

anticoagulant necessary to prevent blood from clotting during the exchange

• Citrate binds ionized calcium, hence hypocalcemia occurs• Symptoms include perioral tingling, numbness• Treated with IV or oral calcium supplementation

Hypotension• Occurs in some patients• Usually mild• Important not to take certain blood pressure medications

prior to plasma exchange (ACE inhibitors)