Wednesday, 28 March 2012

Hemophilia B


Hemophilia B


Hemophilia is a hereditary bleeding disorder.’ [3] Two types of hemophilia A and B are both caused by gene mutation, which is a deficiency of blood clotting factors [3][7]. As the complete treatment to cure disease has not been discovered yet, patients only have to rely on infusion of concentrates so far. These days, however, in the united of Kingdom, it is announced that a cluster of medical researchers have successfully cured six patients suffering from hemophilia B [1].


Figure  1. symptoms of hemophilia

Hemophilia B is even more rare than hemophilia A, and is caused by a deficiency of factor IX, which is blood-clotting agent, officially named as a blood plasma protein in blood.[1][5]. It is usually followed by the symptoms of ‘bleeding into joints, excessive bleeding and bruising’ [3]. Hemophilia B is inheritable as a defective Factor IX in a gene is placed on the X chromosome. For females, even if factor IX is found defective, it can be compensated by the other good copy of X chromosome as they have two copies of X chromosome. The males, however, only have one X chromosome inherited from their mother, and one Y chromosome from their father, meaning that the males are more likely to get this disease [2][3], since there is no more X chromosome to replace a defective gene. Although fathers do not have hemophilia, it can still be inherited by mothers who play a role of carrier if they have hemophilia in their X chromosome [3].





















Figure 2. Female’s role as a carrier of hemophlia [5]

The treatment for hemophilia B is mainly based on gene therapy that uses DNA as a pharmaceutical agent that a defective factor IX is replaced with the correct form of the same gene [1][4]. The researchers have undergone many trials and errors due to the immune system that kills all the delivery viruses that carry the intact copies of Factor IX to replace with the defective one before the genes have an effect on the body [1]. Through many trials, the researchers discovered more effective delivery virus and steroids that prevent the immune system from killing the viruses. The virus used in the treatment is called ‘adeno-associated virus-8’ [1]. This virus functions better in the treatment that other kinds of viruses can randomly invade into chromosomes, making a change in a gene, whereas ‘adeno-associated virus-8 only stays outside the chromosomes’ [1]. Additionally, factor IX is generally produced by liver cells, which are targeted by this virus, it helps the therapy efficient. The negative aspect, however, is that as liver cells do not last eternally the length of time the therapy lasts really depends on liver cells [1].

Even though the treatment for hemophilia B cannot be spread out yet, it is a very significant improvement in the treatment as the patients, in the past, only have to rely on infusion of factor IX concentrates. However, once the treatment the researchers have developed is completed and generalized throughout the world, they will be able to live as normal people.






References

Original article:

[1] Nicholas,W 2011, ‘Treatment for Blood Disease Is Gene Therapy Landmark’, The New York Times, 10 December, viewed 14 March 2012, http://www.nytimes.com/2011/12/11/health/research/hemophilia-b-gene-therapy-breakthrough.html?_r=1&ref=geneticengineering



Other websites used:

[2] ‘National Hemophilia Foundation’, 2006, Hemophilia B, viewed on 16 March 2012, http://www.hemophilia.org/NHFWeb/MainPgs/MainNHF.aspx?menuid=181&contentid=46

[3] ‘The New York Times’, 2008, Hemophilia B, viewed on 16 March 2012, http://health.nytimes.com/health/guides/disease/hemophilia-b/overview.html

[4] ‘Genetics Home Reference’, 2011, Gene Therapy, viewed on 17 March 2012, http://ghr.nlm.nih.gov/handbook/therapy/genetherapy

[5] ‘Nursing Crib’, 2009, Hemophilia, viewed on 17 March 2012, http://nursingcrib.com/nursing-notes-reviewer/maternal-child-health/hemophilia/ (picture)

[6] Robert, Z 2011, ‘Hemophilia B’, Medscape Reference, viewed on 17 March 2012, http://emedicine.medscape.com/article/779434-overview

[7] Victor, S 2011, ‘Hemophilia – Causes, Symptoms, Diagnosis and Treatment’, Doctor tipster, viewed on 18 March 2012, http://www.doctortipster.com/6480-hemophilia-causes-symptoms-diagnosis-and-treatment.html




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