Duchenne Muscular Dystrophy

Posted by Elliot Dubowitch from Drexel University College of Medicine Class of 2014

Duchenne muscular dystrophy (DMD) is one of the four main groups  of muscular dystrophy, a muscle disorder that affects and weakens the musculoskeletal system.

Muscular dystrophies are genetically inherited and progressive.

DMD is inherited in an x-linked manner.  This means that the mother, who is unaffected, is a carrier for the disease and has a 50% chance of passing it on to her male children.

The disease is caused by a deficiency in the Dystrophin protein, a complex that anchors the muscle to surrounding tissue.

dystrophin

This disease has a wide spectrum of symptom severity, depending on the type of genetic mutation, with Duchenne being very severe, and Becker’s muscular dystrophy being much more mild.

The symptoms in DMD are not usually present at birth.  As the child ages, however, they symptoms will gradually become worse and worse.  Most children are unable to walk by thirteen years of age and die in their twenties due to respiratory failure.

One of the earliest signs of DMD is called to as the “Gower Maneuver.”  Although not pathognomonic for DMD, this maneuver is a sign for proximal muscle weakness and is often correlated with DMD.  Below is a clip of a child performing to Gower’s maneuver to stand.  The patient must “walk” up his body using his hands from a sitting position due to weakness in his hip and thigh muscles.  Below is a video clip demonstrating this.

Another early sign is calf pseudohypertrophy.  Although the muscle looks bigger, it is not necessarily stronger, as the functional muscle is replaced by nonfunctional fibrous tissue.

Unfortunately, there is currently no cure for DMD.  However, there is symptomatic treatment available, such as respiratory support, cardiovascular monitoring and treatment and (if needed) surgery for scoliosis.

Steroids are the only current medication that has been shown to keep the boys walking longer.  A study was conducted in which one group of boys were given steroids daily, whereas the other group of boys were given steroids 10 days on and 10 days off.  The boys receiving daily steroids walked on average until the age of 14.5 year, while the boys receiving steroids intermittently walked to only 12 years of age.  The boys receiving continuous steroids also had more side effects including weight gain, mood swings, increase risk of infection, and other side effects of steroid usage.  If one is to consider steroid use, it is imperative to remember that it must be used at the time the child is still ambulating.  The boy will not regain lost function, however he may retain his current function longer.  In the future we hope that new drugs like VBP-15 will hopefully provide the benefits of corticosteroids without some of the side effects.

Genetic research is currently being done to hopefully find a cure for this disease.

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2 thoughts on “Duchenne Muscular Dystrophy

  1. Pingback: Posts about neurology from 2 of our recent medical students | Neurology Update

  2. Pingback: Exon Skipping for Duchenne Muscular Dsystrophy | Neurology Update

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