Plasmapheresis, or plasma exchange, is a treatment commonly used in autoimmune diseases to remove circulating harmful antibodies — known as autoantibodies — that mistakenly recognize the body’s own proteins as foreign.
Lambert-Eaton myasthenic syndrome (LEMS) is caused by autoantibodies that work against a protein, called voltage-gated calcium channel (VGCC), that is found on the nerve cell endings. This prevents the uptake of calcium ions into the nerve cells. That uptake is necessary for the release of the neurotransmitter or cell signaling molecule, acetylcholine, at the neuromuscular junctions — the point where the nerve and the muscle cells meet. Acetylcholine normally binds to acetylcholine receptors situated on the surface of muscle cells, and stimulates muscle contraction. When VGCCs are attacked by autoantibodies, lower amounts of acetylcholine are released from the nerve cells. This leads to symptoms such as muscle weakness and fatigue.
One round of plasmapheresis is estimated to remove 60-70% of the disease-causing autoantibodies in the plasma, or liquid part of the blood. It is generally used to stabilize LEMS patients, and restore the normal signaling between the nerve cells and the muscle cells at the neuromuscular junctions. That, in turn, improves muscle contraction. Â However, plasmapheresis only provides temporary relief and needs to be repeated often. Therefore, it is not the preferred treatment option for people with LEMS, especially considering the potential complications associated with it.
How plasmapheresis works
During plasmapheresis, a patient’s blood is circulated through a machine, which contains a cell separator. The cell separator may work in one of two ways:
- Blood is centrifuged, or spun at high speeds in the cell separator machine, which separates out the blood cells from the plasma, or
- The cell separator may contain a membrane with small pores through which only the plasma can pass. The blood cells cannot permeate through the pores.
The cellular components of blood include red blood cells, white blood cells, and platelets. The plasma contains soluble components of blood, including proteins such as antibodies and blood clotting factors.
The blood cells are then returned to the patient in replacement plasma, which can be fresh or processed donor-derived plasma.
Plasmapheresis and LEMS
There are no reports of randomized, controlled clinical trials evaluating the efficacy of plasmapheresis in people with LEMS. However, there are a few case studies that have been published.
In a study published in the journal Neurology, nine people with LEMS underwent plasmapheresis five to 15 times over a four- to 19-day period. The patients also received immunosuppressive drug treatment (60 to 100 mg of prednisone on alternate days, and 2.5 mg/kg body weight of azathioprine, for 0.5 to 2.5 years). Eight of the nine patients showed improvements in clinical parameters and muscle contraction, based on electromyographic muscle action potential (MAP) amplitude assessments. The most significant response was observed 10-15 days after plasmapheresis. This study suggested that immunosuppressive therapy and plasmapheresis can be beneficial for the symptomatic treatment of LEMS.
In another study, published in the journal Therapeutic Apheresis and Dialysis, the efficacy of plasmapheresis was analyzed in two patients with LEMS based on clinical scoring, electrophysiological findings, and the amount of autoantibody found. In both cases, the amount of autoantibody declined after plasmapheresis, but returned to normal in a week.
The researchers suggested that the benefits of plasmapheresis are transient, probably because of the high rate of production of autoantibodies by the immune cells. These autoantibodies are not cleared by this method, and remain in the patient’s body.
Other details
Although plasmapheresis is a well-standardized procedure, and relatively safe and routine, there could be some adverse effects:
- Plasmapheresis can cause hypotension, or reduced blood pressure, because of a decrease in plasma volume.
- Repeated plasmapheresis can cause alterations in the acid-base balance of the blood, called metabolic alkalosis, which can result in complications. This is mostly caused by the use of sodium citrate during the process, to prevent blood clotting. Sodium citrate also can remove free calcium from the blood, which can lead to hypocalcemia, or low calcium levels. That condition can result in severe muscle cramps. In extreme cases, it also can cause cardiac arrhythmias, or irregular heartbeats.
- Repeated plasmapheresis with albumin replacement can deplete blood clotting factors and antibodies, both of which can increase the risk of bleeding and infections.
- Patients undergoing plasmapheresis have an increased risk of infections and thrombosis.
- In rare cases, there is a risk of virus contaminations when using fresh-frozen plasma as a replacement.
Last updated: July 23, 2019
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