Comedian Gilbert Gottfried has died: What is myotonic dystrophy type II?

Comedian Gilbert Gottfried, known for his distinctive voice, has died at age 67, his family announced Tuesday (April 12) on social media. 

Gottfried’s family did not specify the cause of his death, noting only that he died "after a long illness." However, in a separate statement, Gottfried's friend and publicist Glenn Schwartz said he experienced recurrent ventricular tachycardia, a type of abnormal heart rhythm, due to a genetic condition called myotonic dystrophy type II, according to Rolling Stone.

Myotonic dystrophy type II is a form of muscular dystrophy, a group of progressive diseases that cause muscles to grow weaker and lose mass over time, according to the U.S. National Institutes of Health Genetic and Rare Diseases Information Center (GARD). Symptoms of the inherited condition typically arise in early adulthood, between the 20s and 30s, and the disease is characterized by myotonia, or prolonged muscle contractions, which make it difficult to relax a muscle after you tense it. 

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The disease is caused by mutations in a gene called CNBP, according to GARD. CNBP contains instructions to build a protein that binds to DNA and RNA, DNA's molecular cousin; in binding to these genetic molecules, CNBP helps regulate which proteins the cells build and when, according to the protein sequence database, Uniprot. 

A person needs just one copy of the mutated gene to develop myotonic dystrophy type II, meaning the disease is inherited in an "autosomal dominant" pattern, according to GARD.

The protein encoded by CNBP is mainly found in the heart and in skeletal muscle. When mutated, the CNBP gene causes cells to build dysfunctional messenger RNA (mRNA) molecules that clump together, interfere with the production of other proteins and thus undermine the function of muscle cells, leading to symptoms of muscular dystrophy, according to GARD.

Myotonic dystrophy type II most commonly affects muscles in the neck, fingers, elbows and hips, causing muscle pain and weakness in those areas. Muscles in the face and ankles can also be affected, and more rarely, the condition can cause dysfunction in the cardiac conduction system, the electrical system that controls heartbeat, according to GARD.

These kinds of conduction issues arise from damage to heart muscle cells, which causes the tissue to scar and disrupts the electrical pathways that normally direct the movement of the heart's chambers, according to Johns Hopkins Medicine.

In Gottfried's case, Schwartz said that he experienced ventricular tachycardia, a type of abnormal heart rhythm, or arrhythmia, that occurs when the heart's lower chambers beat too quickly. This abnormal rhythm undermines the heart's ability to deliver an adequate amount of oxygenated blood to the body, according to Johns Hopkins Medicine.

In short, seconds-long spurts, ventricular tachycardia isn't necessarily dangerous. But when the abnormal heart rhythm persists for too long, it can cause lightheadedness and fainting, due to a drop in blood pressure, and it can also cause cardiac arrest and ventricular fibrillation, an extremely rapid and life-threatening type of arrhythmia, according to Johns Hopkins Medicine.

People with myotonic dystrophy type II sometimes require an implantable cardioverter defibrillator (ICD) — a battery-powered device that detects and stops irregular heartbeats using electrical pulses — in order to manage the arrhythmia related to their condition, GARD notes.

Originally published on Live Science.