Myotonic Dystrophy Is a Rare, Genetic Disease—And Its Link to Ventricular Tachycardia Is Even Rarer

Comedian Gilbert Gottfried passed away at age 67 on Tuesday of ventricular tachycardia due to myotonic dystrophy type 2, a little known and very rare condition.

An inherited disease, myotonic dystrophy occurs in about eight in 100,000 people, according to the Centers for Disease Control and Prevention (CDC). Myotonic dystrophy type 2, is an even rarer form of the the condition and its exact prevalence is unknown.

Here's a closer look at myotonic dystrophy type 2, including its often overlooked symptoms and its link to ventricular tachycardia.

Myotonic Dystrophy Type 2 and Recurrent Ventricular Tachycardia

Myotonic dystrophy type 2 typically impacts muscles throughout one's body, including those in the neck, fingers, elbows, and hips, as well as facial and ankle muscles, according to the Genetic and Rare Diseases Information Center (GARD). Individuals with the condition may experience prolonged muscle tensing—known as myotonia—as well as muscle weakness, pain, and stiffness, according to GARD.

A genetic disease, myotonic dystrophy type 2 is inherited and is caused by mutations in the CNBP gene, though the exact function of this gene is not known. The severity of the disease can vary significantly among those who are affected, even within the same family.

Myotonic dystrophy may also impact other body systems–such as the heart–which was the case with Gottfried, who had been suffering from recurrent ventricular tachycardia, PEOPLE reported.

"Ventricular tachycardia is one of the abnormal heart rhythms that is known to occur with myotonic [patients], both type 1 and type 2," Elizabeth McNally, MD, PhD, professor and director at Northwestern University's Center for Genetic Medicine, told Health. "The electrical system of the heart is directly affected by the genetic change that causes myotonic [dystrophy]."

Ventricular tachycardia is a major cause of sudden cardiac death, according to MedlinePlus.

The heart condition Gottfried experienced is so rare, however, that researchers don't have specific numbers detailing how many myotonic dystrophy type 2 patients are diagnosed with the extenuating ventricular tachycardia.

"It's hard to give an exact percentage about how many myotonic patients develop this complication, [but it's] definitely the minority of patients," Dr. McNally said.

Warning Signs of Myotonic Dystrophy Type 2

Myotonic dystrophy may go undiagnosed for years, if not decades, because the signs may be simply overlooked earlier in life, and later in life they may be associated with aging. But importantly, symptoms of myotonic dystrophy can start occuring in a person's twenties and become more pronounced later in life, according to GARD.

"The weakness may not show up until people are in their sixties, in which case, they may incorrectly attribute the muscle weakness to normal aging," said Dr. McNally.

The heart problems associated with myotonic dystrophy type 2 may also be credited to simply being part of older age, Dr. McNally added: "The heart problems also can go unnoticed since the symptoms might be considered fatigue or inability to exercise as much as they once did."

The telltale sign of myotonic dystrophy type 2 is muscle wasting and weakness. Patients with myotonic dystrophy type 2 often experience prolonged muscle contractions and sometimes have difficulty relaxing certain muscles, which makes everyday tasks like releasing one's grip on a doorknob challenging.

The condition may also cause:

• Slurred speech and temporary locking of the jaw
• Abnormalities of the electrical signals that control the heartbeat (a less common symptom)
• Clouding of the eyes (called cataracts)
• Diabetes

Additionally, men with the condition sometimes experience balding and infertility, according to the GARD.

"For myotonic dystrophy type 2, the most common first sign is weakness of the muscles—especially in the thighs—where people may notice it gets difficult to climb stairs without grabbing hand rails," Dr. McNally said. "People will also notice it gets difficult to get up from a chair unless they can also push up with their arms."

How and When Myotonic Dystrophy Patients Are Usually Diagnosed

While it may be an often overlooked condition, those who have a family history of the disease may get an earlier diagnosis. If a person knows they're related to someone who suffered from the condition, they may be more likely to undergo genetic testing to determine whether they have it as well.

When a patient presents with the symptoms of myotonic dystrophy type 2, the first step in confirming a diagnosis might be a blood test. "At the doctor's office, blood tests can show elevated muscle markers, and this can be a tip off that something more [than regular aging] is going on," Dr. McNally said.

The disease can also be diagnosed through a physical exam, according to GARD, which explains that such an exam might: "identify the typical pattern of muscle wasting and weakness and the presence of myotonia," adding that "a person with myotonic dystrophy may have a characteristic facial appearance of wasting and weakness of the jaw and neck muscles."

The definitive myotonic dystrophy type 2 test is genetic testing, according to the GARD. For this test, a blood sample is analyzed to look for a gene mutation that signals the condition.

Prognosis and Treatment Options

There are various management strategies to address myotonic dystrophy. Based on the symptoms of the affected individual the treatments can include relying on ankle-foot braces or wheelchairs, having cataracts removed to improve vision, and defibrillator placement (if the patient suffers from arrhythmias), according to GARD.

Routine exercise may also provide some relief and help with both controlling pain and enhancing muscle strength and endurance. Additionally, testosterone replacement therapy may be suggested to males with myotonic dystrophy type 2.

Because the symptoms of myotonic dystrophy type 2 are usually relatively mild, and progress slowly, patients with myotonic dystrophy type 2 are often able to walk until they reach their sixties. However, in some cases, it can impair mobility earlier in life.

When compared to myotonic dystrophy type 1, the type 2 form of the disease is typically milder and will not necessarily shorten one's lifespan, according to GARD. Though as myotonic dystrophy passes from one generation to the next, it often begins earlier in life its signs and symptoms become more severe.

While there is no cure for the disease, researchers are working to develop treatments.

"There are now multiple therapies in preclinical and early-phase clinical testing for many neuromuscular diseases, including myotonic dystrophy," said Dr. McNally.