Myasthenia gravis (MG) is the most common disorder of neuro-muscular junction transmission that presents in various ways among the people it affects. There are about 10 to 20 new cases diagnosed each year per million, with more than 150 people per million affected with the disease. Forty years ago, mortality from this disorder was nearly 70 percent; today it is less than 5 percent.
More common in females than males, MG has a bimodal distribution: one between the ages of 20 and 30 and another peak in the sixties to eighties, especially in men at the older ages.
MG is best described as a varying and episodic weakness of voluntary skeletal muscles in the body. Most affected are the muscles of the eye, face, neck, tongue, lips and throat. Muscles in the limbs and trunk are affected, but less commonly.
Muscle weakness is often worse after exercise or toward the evening. Fluctuating weakness of commonly used muscles causes symptoms such as double vision, eyelid drooping and difficulty in swallowing. When respiratory muscles are affected, the disease is potentially fatal without mechanical breathing intervention.
There are two main forms of the disease: (1) ocular (affecting the eye) and (2) a generalized type. Drooping eyelids and double vision can run the gamut from mild to disabling with ocular MG. The generalized type starts with ocular symptoms and eventually spreads to muscles in the face, limbs and trunk, and those involved in speech, chewing and swallowing.
A more severe type involves weakening of the respiratory muscles to the point that breathing is paralyzed. Death can occur from pneumonia secondary to inhaled pathogens or respiratory complications where machine assisted breathing becomes predominant.
One other form worth mentioning is called Eaton–Lambert myasthenia syndrome and usually is accompanied by oat cell cancer of the lung or other tumors. Myasthenia is sometimes the first sign of involvement and cancer is then discovered on a full work-up.
While quite involved, MG is usually thought of as an autoimmune disorder in which the body mistakenly begins to produce antibodies that interfere with transmissions at most normal nerve endings, preventing motor nerves from contracting. Eventually the receptors are so severely attacked that the place of interaction for muscle stimulation is destroyed. Without specific treatment, the disease can take a progressive downhill course unless it is mild or confined only to the eyes.
Diagnosis is often made on a description of symptoms from the patient, along with physical signs and a thorough history. Many investigational tests such as the acetylcholinesterase test, blood testing, and the presence of acetylcholine receptor antibodies confirm the disease.
MG usually follows a characteristic course of remissions and relapses. Highest mortality is usually seen early in the disease, in severe cases within the first year and with progressive cases within the first five to seven years. Respiratory complications are the most common issues.
With such a serious disease, can insurance be offered?
• When the disease is mild, non-progressive, limitations are minor and patients respond to specific medication such as anticholinesterases, a case can be slightly rated substandard.
• When the ocular form can persist without systemic issues and those who are maintained without medicine or go into remission can sometimes be standard issues.
• In the generalized form where there is progression and in whom respiratory complications occur, the overall prognosis is the most grave.
