Muscles

Loss of muscle strength and function is progressive in Duchenne patients. Dystrophin helps maintain and heal muscle after normal use. With little to no dystrophin production, Duchenne muscles are damaged and replaced by connective tissue and fat. Early on, common motor skills are delayed, followed by slow weakening of the core skeletal muscle in early childhood. This loss of muscle strength spreads to the lower and upper limbs in adolescence, taking away the ability to walk and to perform essential daily living tasks independently such as dressing, eating, and bathing.

Current Standard of Care:

• Regular evaluation by a neuromuscular doctor to measure strength and function
• Steroids in the form of prednisone or deflazacort to prolong ambulation
• Daily stretching and/or night splints to keep the ankles loose
• In boys with a certain kind of mutation, use of an exon skipping agent

What’s Going on in Research:

• Continued development of exon skipping and read-through agents for boys with specific kinds of mutations
• Anti-fibrotic and anti-inflammatory drugs are being developed to minimize the development of scarring in the muscles
• Utrophin upregulation, which would act like a dystrophin substitute
• Myostatin inhibition, which would allow muscles to grow bigger and stronger
• Steroid alternatives, which would aim to spare boys from the side effects of traditional steroid use
• Gene therapy, which is a technology that can be used to deliver a variety of different gene substitutes to the body’s muscles. A variety of mechanisms can be utilized with this kind of therapy
• CRISPR-Cas9 is a revolutionary concept that allows for gene editing, which could potentially correct the genetic error that causes DMD. This technology has a long way to go before it reaches clinical trials, but it is both promising and very exciting!

Bone

Duchenne patients typically have weakened bones and low levels of Vitamin D at onset. Steroids, commonly prescribed to address the skeletal muscle impacts, contribute to poor bone health by decreasing the calcium levels in bones. Over time, bones thin and become more brittle, leading to serious bone health issues, such as osteoporosis. This makes those living with Duchenne at high risk for fractures and breaks, which can have devastating impacts. With weakened skeletal muscles in the back, Duchenne patients are susceptible to scoliosis and compression fractures, often requiring serious, corrective surgery. Lastly, joints in feet, knees, elbows, etc. can become locked in one position as loss of ambulation occurs.

Current Standard of Care:

• Regular bone density scans (DEXA scans, or densitometry), especially if your child is on steroids, will let the care team monitor how healthy his bones are and provide treatment if needed
• Vitamin D and calcium labs; both vitamin D and calcium are known to play a role in bone health. If levels are low, supplementation is easy and often available in the form of gummies or chews
• If bone density gets too low, different medications can be given that increase bone density. Some are in the form of a once-weekly pill, while others are IV infusions a few times each year

What’s Going on in Research:

• When muscles are weak, they don’t put enough stress on the bones, which leads to decreased bone density. By improving muscle bulk and function, bone health should benefit secondarily

Brain

A small amount of dystrophin exists in the brain. Without it, people living with Duchenne are more likely to have development delays in learning, behavior, and social/emotional health compared to their peers. Specifically, this can lead to weakness is executive function skills, such controlling impulses and emotions, flexible thinking, and working memory, and trouble with friends or in a school/learning environment. For patients and caregivers, this can often feel like the most complex and troubling impact to manage among Duchenne patients. Not only is the spectrum of psychosocial health so vast, but ensuring overall well-being and self-image is important as patients adjust to the stages of Duchenne and seek support from those around them.

Current Standard of Care:

• If necessary, neuropsychology evaluations can be extremely helpful in assessing the best way your son can learn, giving him the tools to be successful at school and in the community
• Since some boys with Duchenne have trouble focusing, screening for ADD, ADHD, and other cognitive and behavioral disorders is important
• Individualized education plans (IEPs) can be helpful to have in place at school; IEPs allow families and schools to work together to make sure any accommodations or special needs are addressed and available to promote success at school

Heart

Your heart is a muscle too. The lack of a sufficient amount of dystrophin leads to weakening and scarring of the heart muscle. Although progression varies, heart disease will eventually affect all those living with Duchenne. The heart’s ability to pump blood properly throughout the body is impacted. Changes to heart rate and/or rhythm can also occur as patients with Duchenne get older. Damage to the heart, otherwise known as cardiomyopathy, begins in early stage before symptoms even appear. Cardiomyopathy and heart failure are the leading cause of death in Duchenne patients.

Current Standard of Care:

• Annual cardiac screening, either by echocardiogram or cardiac MRI and EKG to monitor for changes in the heart’s structure or rhythm
• ACE inhibitors and beta-blockers to reduce the workload on the heart and minimize fibrosis
• Later in the disease process, devices to help regulate the heart’s rhythm and pumping function can be used

What’s Going on in Research:

• Aldosterone inhibition through use of spironolactone and eplerenone, which are drugs used to treat other heart conditions and thought to be beneficial in DMD
• Other treatments aiming to decrease or reverse fibrosis are also under investigation

Lungs

Weakening of those muscles around the lungs that are critical to breathing, including the diaphragm, makes it difficult for those living with Duchenne to breathe and cough. Duchenne patients eventually breathe at an abnormally slower rate, increasing the amount of carbon dioxide in the blood. Breathing and coughing typically start to become problematic after the loss of ambulation occurs between the ages of 8-12. Patients may need to begin to use a breathing assist machine at night as teenagers, progressing into full time breathing assist or ventilation machines as young adults.

Current Standard of Care:

• Regular pulmonary function testing to monitor lung strength and capacity
• Regular use of a cough assist device as a kind of “physical therapy” for the lungs; usually prescribed by your doctor in the middle school years
• Sleep studies as recommended by you pulmonologist to monitor for sleep apnea or other sleep problems that could impact breathing
• Sleep aids, like BiPAP, if indicated by a sleep study and/or your pulmonologist
• Pneumonia vaccination to lower the risk of lung infections

What’s Going on in Research:

• Many studies, including cardiac and skeletal muscle studies, include pulmonary function testing in their measurement of drug efficacy. Drugs that express in the skeletal muscle will hopefully express at high levels in the muscles that support lung function, too, leading to improved pulmonary function