Looking for a better treatment for the autoimmune disease myasthenia gravis, researchers have found that a protein in tick saliva shows promise in limiting the severity of the disease in an animal model in a study published in the Annals of Neurology.
"This disease can leave patients weak and on breathing machines, and conventional treatments can be toxic," said Henry Kaminski, M.D., chair of the department of neurology and psychiatry at Saint Louis University and one of the nation's leading experts on myasthenia gravis. "There is a real need for better treatments. This study is a step in that direction."
Myasthenia gravis is a highly debilitating, chronic neuromuscular disorder that affects about 400 to 600 per 1 million people, and roughly 1,100 to 1,700 people in the St. Louis area. Symptoms include weakness in the arms and legs, chronic muscle fatigue, difficulty breathing, difficulty chewing and swallowing, slurred speech, droopy eyelids and blurred or double vision.
While drugs like prednisone, a corticosteroid, can be effective in treating the disorder, they also can carry a host of severe side effects, including pronounced weight gain, osteoporosis, glaucoma and diabetes.
Other treatments, intravenous immunoglobulin and plasmapheresis, which involve blood plasma, are expensive and can have rare but serious side-effects such as infections, heart attacks and stroke.
Doctors believe that myasthenia gravis is caused by an overreaction of the complement system, a component of the immune system that specifically defends against parasites, bacteria and other pathogens. Antibodies block nerve receptors at the neuromuscular junction, the place where nerves connect with muscles, and then activate complement which prevents muscle contraction from occurring, causing weakness.
To impede the complement system's misplaced response, researchers hope a new class of drugs, called complement inhibitors, may stop the body's defense system from attacking itself.