Rare Disease Report

Duchenne Muscular Dystrophy - Rare Disease Quick Facts

JULY 18, 2013
rarediseasereport

Duchenne muscular dystrophy is a fatal genetic disorder diagnosed in childhood, affecting approximately 1 in every 3,500 live male births (about 20,000 new cases each year). Duchenne can also occur in females but it is not as common since the condition is due to a mutation of a gene on the X-chromosome (females have two X-chromosomes so the odds of having mutations on both is extremely rare). 

Pathophysiology

  • Duchenne is caused by a mutation in the gene that encodes for dystrophin, a protein that helps maintain muscle cell structure. Without dystrophin, muscles are unable to operate properly, suffer progressive damage and die
  • The progressive muscle weakness leads to serious medical problems (cardiac and respiratory). Young men with Duchenne typically do not live past their twenties
  • There are several mutations of the dystrophin gene that can lead to Duchenne
  • The dystrophin gene is carried on the X-chromosome. Girls have two X-chromosomes so if one has a mutated dystrophin gene the other chromosome can compensate. The same is not true for boys
  • Duchenne is thought to be passed from parent to child but many cases occur in families without a history of Duchenne.

Symptoms
Early Phase (diagnosis to age 7)

  • Move slower and appear clumsy. Difficulty climbing, jumping, running
  • Fatigues easily
  • Some muscles (in particular his calves) may appear enlarged or overdeveloped
  • Learning difficulties and slower development

Transitional Phase (ages 6 to 9)

  • Walk on the balls of his feet or toes to help stay balanced
  • May stick out belly and throw shoulders back as he walks
  • “Gower maneuver”
  • Fatigues easily. May require a stroller, lightweight wheelchair, or electric scooter for longer distances

Loss of Ambulation (ages 10 to 14)

  • Rapid deterioration of walking ability occurs during this stage
  • Activities involving the arms, legs, or trunk will require assistance or mechanical support
  • Scoliosis
  • Fatigues easily

Adult Stage (ages 15+)

  • Life-threatening heart and respiratory conditions more prevalent (shortness of breath, fluid in the lungs, swelling in the feet and lower legs, enlarged heart)

Treatment

  • There is no known cure for Duchenne muscular dystrophy and current treatment is centered on making the patient more comfortable and/or deter muscle weakness progression (steroids, assisted ventilation, cardiac medications, physical and speech therapy). 

Orphan Drugs

  • There are currently no orphan drugs approved for treating Duchenne. However, there are currently 27 orphan drugs designated for treating Duchenne. 
  • 4 drugs that are currently ending phase 2 or starting phase 3 studies include:

Advocacy groups (there are several - below are some of the bigger groups)

 

image of mucsle cell courtesy of wikimedia commons.



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