Duchenne Muscular Dystrophy

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Duchenne muscular dystrophy (DMD) is one of many types of muscular dystrophy. Muscular dystrophy is a genetic condition that is characterised by the degeneration of muscle tissue and increased susceptibility to damage, it progressively worsens throughout a sufferers life.

Symptoms can be spotted from early infancy (anthing before 6 years old), walking usually becomes difficult around the age of 12, and around the age of 20 problems with the heart and breathing will occur.[1]

Contents

Cause

DMD is caused by a mutation in the dystrophin gene, the largest known gene in the human genome, the mutation leads to a non-functional dystrophin protein being synthesised[2]. Dystrophin is essential in muscles and without the protein, the muscles will deteriorate and eventually resulting in death, usually in the first two to three decades of a sufferers life, this is due to the cardiac muscles, as well as those associated with breathing, eventually failing.

It is X-linked recessive and so is only passed on if the mother is a carrier. This is also why sufferers will usually be boys because they only have one X chromosome, and so if that is mutated they do not have another to compensate. It is very rare that a girl will show problems but they can be a carrier. [3]

Treatment

There is currently no permanent cure for muscular dystrophy, there are, however a wide range of treatments designed to help minimise the effects of the disease and increase the patients quality of life.

Some of these treatments are changes to lifestyle, for example, light exercises such as swimming can help to lessen the effects. There are also some drugs that can be used to treat the condition, such as steroids. Steroids can help to reduce the rate of muscle loss and are effective for six months to two years.[4] Beta blockers and ACE inhibitors can also be used to treat heart failure. There can also be surgery to correct things such as scoliosis. However, these things are not cures, they are just things to help.[5]

Creatine can also be taken to help lessen the effects of the condition, it helps to improve muscle stregnth while causing very few side effects.[4]

A recent study from October, 2015, has yeilded positive results into the posibility of long term treatment of sufferers of DMD. Genetically removing of the P2X purinoceptor 7 protein in DMD mice has resulted in the reduction of several sypmtoms of DMD 'In dystrophic muscles at 4 wk there was an evident recovery in key functional and molecular parameters such as improved muscle structure (minimum Feret diameter, p < 0.001), increased muscle strength in vitro (p < 0.001) and in vivo (p = 0.012), and pro-fibrotic molecular signatures. Serum creatine kinase (CK) levels were lower (p = 0.025), and reduced cognitive impairment (p = 0.006) and bone structure alterations (p < 0.001) were also apparent.' (Anthony Sinadinos et al, Oct 2015). [6] The removal of the protein was made possible by mating mdx Mice (affected) with mice that do not have the gene that codes for P2RX7, resulting in offspring with a non-functioning form of the protein. Although no clinical trials have taken place, the use of P2RX7 antagonists my be able to increase the quality of live from DMD sufferers. [7] 

The Future

More recently, genetic treatments are being developed to try and cure the disease entirely, this has not yet been successfull but it is hoped that with continued research the dystrpohin gene can be replaced in it's entirety for a functioning copy.[8]

References:

  1. https://www.nlm.nih.gov/medlineplus/ency/article/000705.htm
  2. http://jp.physoc.org/site/misc/editorinterviews.xhtml#kdavies
  3. https://www.nlm.nih.gov/medlineplus/ency/article/000705.htm
  4. 4.0 4.1 http://www.nhs.uk/Conditions/Muscular-dystrophy/Pages/Treatment.aspx
  5. http://www.nhs.uk/conditions/muscular-dystrophy/Pages/Introduction.aspx
  6. http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001888
  7. http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001888
  8. http://www.ncbi.nlm.nih.gov/pubmed/18422374

<(Anthony Sinadinos et al, Oct 2015) DOI: 10.1371/journal.pmed.1001888/>

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