Worsening of Heart Function Observed in Duchenne Muscular Dystrophy Patients

Acceleration in the decline of heart function in patients with Duchenne muscular dystrophy (DMD) was seen due to a mutation in the gene which causes cystic fibrosis, said researchers at UT Southwestern. This research will help doctors to extend patients lives by developing new strategies to preserve the heart function in this population of patients. These findings were published in the journal of the American Heart Association.

Duchenne Muscular Dystrophy is an inherited disorder of progressive muscular weakness which affects 1 of every 3,500 to 5,000 in males all over the world, which is caused by a mutation on the X chromosome.

The progressive muscle weakness is caused by mutation in the protein which protects muscle cells from damage called dystrophin. The reason for death in these patients usually before the age of 35 is cardiomyopathy or weakness of the heart muscles though these patients also suffer from a variety of lung and neuromuscular complications.

Pradeep Mammen, M.D. who is the associate professor in the department of internal medicine’s division of cardiology at UTSW and is the doctor who runs the cardiology clinic specifically for the patients with DMD and other neuromuscular disorders has said that that all the patients with DMD will eventually develop cardiomyopathy but how early it will develop and how progressively it manifests will vary considerably.

Although the reason for the variability is unknown, Mammen and his colleagues have suspected that it might be the result from an additional genetic variation, which accelerates the worsening of heart failure in DMD patients.

Mammen and his colleagues recruited 22 males who have DMD and 12 female carriers, mostly mothers of these patients to search for the genetic variants which has this effect. Cardiac magnetic resonance imaging (cMRI), cardiac computed tomography or echocardiography was used to assess the cardiac function in almost 32 of the volunteers. Additional markers of cardiac function and whole exome sequencing which is genetic test that reads all the protein-making genes in the body were also done by collecting blood samples from the volunteers.

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The researchers identified a few candidate genes particularly a switch in a single unit of cystic fibrosis transmembrane regular (CFTR) gene also known as ‘missense’ mutation was seen in patients with worst cardiac function. Cystic fibrosis is caused by this gene and in heart cells it regulates the cell electrolyte level.

Mammen said doctors who treat patients with DMD will soon start test to identify patients with mutation in gene to identify and treat patients who need aggressive care at a young age.

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According to current guidelines, DMD patients receive various interventions ranging from drugs like ACE inhibitors, beta blockers and mineralocorticoid receptor agonists to left ventricular assisting devices to treat cardiomyopathy as it develops and worsens.

In normal conditions, patients begin receiving cardiac care in their early teens to early 20s, however the patients carrying the CFTR mutation can benefit from starting aggressive care early to prevent heart damage.

Mammen who holds the Alfred W. Harris M.D Professor in Cardiology has said, “Even with new strategies to treat these patients on the horizon, such as genome editing that could convert DMD to a less severe form known as Becker’s muscular dystrophy, cardiomyopathy will continue to be a patient’s most serious and life-ending consequence. Finding ways to help preserve heart function over time could offer new hope for patients with DMD.”

Source-Medindia