ORLANDO, Florida—Susan Finazzo, 39, is a healthy, active mother of 2 boys with Duchenne muscular dystrophy (DMD). She knows that, as a carrier of DMD, chances are good that she’ll have cardiac problems later in life.
Yet Finazzo, who attended the recent CureDuchenne 2022 Futures conference here, said a well-regarded cardiologist she visited near her home in Miami, Florida, was reluctant to even do an MRI—and only went ahead with the procedure after she insisted.
“I pushed and finally he did the MRI,” she recalled. “After he got the results, he said, ‘maybe we saw something, but we’re not sure. You could just have a cold or an infection. How about we redo the MRI a year from now?’”
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Not satisfied, Finazzo visited a specialized clinic in Texas, presented herself as a carrier of Duchenne, and asked a clinician there if she should be on any particular medication or make any lifestyle changes.
“He laughed at me and said ‘no, just keep doing whatever you’re doing. Live your life,” Finazzo said. “You know, there’s a whole roomful of mothers here who feel the same as I did: that we’ve not been taken seriously. There’s not enough studies done, and not enough information out there. We always put our boys first.”
That is indeed the case, says Pradeep Mammen, MD, professor of internal medicine and director of UT Southwestern’s neuromuscular cardiomyopathy clinic in Dallas, Texas.
“This disease is transmitted in general from mother to son because it’s an X‑linked disease. Most of the previous data was really from the pediatric world,” he told Rare Disease Advisor. “Over the last 20 years, as DMD boys are becoming adults, this disease is now being managed a lot by adult cardiologists and neurologists. We are following many of these carriers, and we’re learning that for many of them, as they age, their hearts are affected.”
Screening Highly Recommended for Mothers of Boys With DMD
Dr. Mammen, who is also codirector of UT Southwestern’s Senator Paul D. Wellstone Muscular Dystrophy Center, follows 950 to 1000 patients with muscular dystrophies of all types and has done extensive research on DMD-associated cardiomyopathy. He said about two-thirds of Duchenne cases are passed from mother to child; the remaining third are de novo mutations.
“Not all Duchenne patients have a mother who’s a carrier, but that’s why it’s important to get tested,” he said. “If they’re a carrier, they really need to be screened to comprehensively assess their cardiovascular status. We have drugs and medications that can delay or prevent development of cardiomyopathy if started early in their lives.”
In fact, he said, “we can now treat even before you start having heart failure; all the more reason you need to get assessed.”
Even so, he said, “I know 2 carriers who made active decisions to have another child. They can screen your eggs to exclude the ones carrying DMD. There are ways to get pregnant and make sure you don’t have a boy with DMD.”
To that end, CureDuchenne has established a data-integrated biobank—open to any mutation, age or mobility status— that helps scientists unlock new treatments.
Blood samples are taken twice a year from those with Duchenne, and once a year from carriers, while urine, saliva, skin, and muscle samples are taken once per year from both groups. Participants also answer annual surveys on quality of life, healthcare usage, and other topics.
“We’re collecting data on female carriers. Women who donate blood and urine to our biobank know they’re carriers,” said Heather Medlin, senior director of clinical operations at CureDuchenne Link, as the biobank is known. Medlin said her goal is to have 5000 people in the database: two-thirds of them boys with Duchenne, and the other third female carriers.
Female Duchenne Carriers Risk Heart Failure
Throughout his career, Dr. Mammen has seen female patients as young as 15 years old, and as old as 70. Generally, they’re referred to him by neurologists or internists, or by word of mouth through nonprofit groups like CureDuchenne. Surprisingly, some of their primary care doctors don’t always know these women may have a son with DMD.
About half of all female carriers will develop some type of cardiac issue in their lives, he said, and two-thirds will develop scarring in the heart, “which is an early sign that the heart is not normal.”
Sometimes, these women show up in Dr. Mammen’s clinic in their 50s and 60s, long after their sons have died from Duchenne—because they never had the normal symptoms of heart failure.
“Ten or 15 years ago, adult cardiologists or heart failure cardiologists were notorious for not taking very extensive family histories. We just said, ‘We don’t know why you have heart failure, but your heart failure is progressing,’” he said.
Dr. Mammen added: “In the last decade, we’ve started linking genetic diseases like Duchenne to development of heart failure. And now it’s becoming more and more known that we need to screen females who come to us for evaluation.”
What about the daughters of such women? Should they be screened too?
“A lot of patients ask me that question,” Dr. Mammen said. “I can’t make that decision for you. If they’re above 18 years old, I say absolutely yes. If your daughter is less than 18, it’s a personal decision between the parents and the daughter whether to screen, find out the mutation and to see a cardiologist. There’s a lot of implications by knowing you’re a carrier, not only for that young child but from an insurance standpoint and all that. But I leave it up to the family to decide.”
