What is myasthenia gravis, the condition that contributed to Jerry Blavat’s death?

Philadelphia icon Jerry Blavat, who died Friday at 82, had an autoimmune condition called myasthenia gravis.

The rare condition was a primary cause of the popular DJ’s death, along with other health problems, according to close friend A.J. Mattia and Keely Stahl, Blavat’s companion of over 30 years.

People with myasthenia gravis experience muscle weakness as a result of antibodies that disrupt communication between muscles and the nervous system.

While there is no cure for the disease, patients can live for many years with proper treatment. In severe cases, a person with the condition can experience a myasthenic crisis, in which the muscles that control breathing become too weak to function.

Here are the basics on the disease, with an assist from Penn Medicine neurologist Shawn Bird, head of the myasthenia gravis clinic at the Hospital of the University of Pennsylvania.

Myasthenia gravis affects muscles over which people have voluntary control, especially those that control the eyes, mouth, throat, and limbs, according to a primer from Johns Hopkins Medicine.

It can result in drooping eyelids, double vision, trouble swallowing and speaking, fatigue, and weakness. As those symptoms can be caused by other diseases, a medical exam is essential for proper diagnosis.

When muscles in the face are affected, a person’s smile “may appear more like a snarl,” according to Johns Hopkins.

A diagnosis of myasthenia gravis is based on the patient’s symptoms and the results of a variety of tests, said Bird, a professor at Penn’s Perelman School of Medicine.

Physicians order blood tests to look for specific antibodies that interfere with communication between the nerves and muscles. They also can measure the electrical activity in muscles with test called an electromyogram, he said.

Some patients may have abnormalities in a gland called the thymus, which can be identified with a CT scan.

The disease can occur at any age, but is more often seen in younger women and in men age 50 and older, according to Hopkins. An estimated 14 to 20 out of every 100,000 people develop the disease, though it is thought to be underdiagnosed, according to the Myasthenia Gravis Foundation of America, an advocacy and support group for patients and their families.

Autoimmune conditions are those in which the immune system responds inappropriately, targeting the person’s own body. The word comes from the Greek root auto, meaning self. (Like something that runs on autopilot — by itself.)

In the case of myasthenia gravis, the immune system produces antibodies that block or destroy certain critical protein structures on the person’s muscles that are called receptors.

These receptors are designed to receive a type of nerve signal (neurotransmitter) called acetylcholine, according to the Mayo Clinic. When receptors are blocked, the signal doesn’t go through, resulting in weakness.

In some people with myasthenia gravis, other antibodies and proteins may be involved.

The condition does not appear to have a genetic component, and it is not clear what triggers it, Bird said.

He likened it to a short circuit, with the result that the immune system no longer recognizes these muscle receptors as being part of the self.

“You don’t recognize that as part of you, and you’ll start to make antibodies against it,” he said.

Yes. A few decades ago, people with myasthenia gravis were more likely to die at an early age. But thanks to advances in treatment, life expectancy is now close to normal in developed countries.

“It’s very rare to have someone die from it,” Bird said.

But a patient can die from the disease if it sets off a cascade of other events, or if the person has other underlying conditions, he said. One example: A person whose swallowing muscles are weak may aspirate small particles of food into the lungs, leading to pneumonia.

Myasthenia gravis is typically treated with medicines called anticholinesterases. Doctors may also prescribe steroids or other drugs that suppress the immune system’s response.

In some cases, surgeons may alleviate symptoms by removing the thymus, though the role of that gland in myasthenia gravis is not fully understood.

Patients who experience trouble breathing should seek emergency care. In severe cases, they may be placed on a ventilator. Physicians then can pump the person’s blood through a device that filters out the problematic antibodies, and they generally recover the ability to breathe on their own, Bird said.

Staff writer Dan DeLuca contributed to this article.