Hermansky-Pudlak Syndrome and the Lysosome

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Last updated 6 years ago

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Science
Subject:
Human Anatomy
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Hermansky-Pudlak Syndrome and the Lysosome

Hermansky-Pudlak Syndrome

IncidenceHermansky-Pudlak syndrome is a very rare disorder in most populations. It is estimated to affect only 1 in 500,000 to 1,000,000 individuals worldwide. However, this disorder is much more common in the country of Puerto Rico than anywhere else in the world. In Puerto Rico, particularly in the northwestern area of the country, nearly 1 in every 1,800 people are affected. It is also believed that 1 in every 21 individuals of northwest Puerto Rican descent are carries of the Hermansky-Pudlak syndrome gene. Although Puerto Rico clearly has the most susceptibility and highest rate of affected individuals, several people with Hermansky-Pudlak syndrome have also been identified in India, Japan, the United Kingdom, and Western Europe.

Hierarchy of Structures AffecedThe three structures most significantly affected by Hermansky-Pudlak syndrome are the integumentary system, nervous system, and respiratory system. The disorder is caused primarily by lysosome-related organelles, or LROs. These LROs that are related to Hermansky-Pudlak syndrome are identified in pigment-producing cells called melanocytes. Abnormalities in the melanocytes can affect the entire integumentary system by making the pigmentation of the hair and skin much lighter. These same LROs affect the pigmentation and sensitivity of retinal tissue in the eyeball. Involuntary eye movements are also a result of this, showing the connection to the nervous system. The LROs involved with Hermansky-Pudlak syndrome are also present in lung cells. These abnormal lung cells cause scar tissue to form in the lungs, which ultimately affects the entire respiratory system by causing a deadly disease called pulmonary fibrosis.

Organelle Affected by DiseaseHermansky-Pudlak syndrome is most closely connected to the lysosome and lysosome-related organelles. Lysosomes are membrane-bound organelles containing digestive enzymes and acid for breaking down and recycling proteins and other cellular waste materials. Lysosomes are related to a group called lysosome-related organelles (LROs), which include melanosomes, lytic granules, MHC class II compartments, platelet-dense granules, basophil granules, azurophil granules, and Drosophila pigment granules. LROs are very similar to lysosomes, but perform additional specialized functions such as pigmentation (melanosomes) and blood-clotting (platelets). Mutations in the genes associated with Hermansky-Pudlak syndrome prevent the formation of LROs or impair their ability to function. Abnormalities or mutations in both lysosomes and lysosome-related organelles are what can lead to Hermansky-Pudlak syndrome, demonstrating the close relationship and connection between these two organelles.

What are the Symptoms?Some prominent symptoms of Hermansky-Pudlak syndrome include a condition called oculocutaneous albinism, problems blood clotting, and breathing problems due to a lung disease called pulmonary fibrosis. Oculocutaneous albinism is a condition that causes abnormally light pigmentation of the skin, hair, and eyes. A person affected by this condition will typically have fair skin and white or light-colored hair. Affected individuals have a high risk of skin damage and skin cancer, reduced vision due to light-sensitive tissue in the retina, and involuntary eye movements. People with Hermansky-Pudlak syndrome also have problems with blood coagulation, which leads to easy bruising and prolonged bleeding. These individuals can also develop pulmonary fibrosis, which causes scar tissue to form in the lungs. This disease usually appears in a person’s early thirties and rapidly worsens, which typically leads to the affected individual’s death within a decade after they first begin to experience breathing problems. Less common symptoms of Hermansky-Pudlak syndrome include inflammation of the large intestine and kidney failure.

Treatment OptionsOculocutaneous albinism, probably the most noticeable symptom of Hermanksy-Pudlak syndrome, is unfortunately untreatable since it is a genetic disorder, which in this case is inherited in an autosomal recessive pattern. However, the problems with blood clotting that many affected individuals experience has a few different treatment options. One option to prevent the excessive bleeding is a blood transfusion with healthy blood platelets that will more easily coagulate. Another option that has proved effective for many patients is a drug called desmopressin acetate. Women with Hermansky-Pudlak syndrome typically experience excessive menstrual bleeding, which can be treated with oral contraceptives. Individuals who have trouble with blood clotting are also advised to avoid blood anticoagulants, such as aspirin.

Other Important InformationWhile pulmonary fibrosis occurs nearly 100% of the time in an individual affected by Hermansky-Pudlak syndrome, although the age it begins to show itself varies. The average age for symptoms of pulmonary fibrosis to appear is during the mid-thirties.There have been eight successful lung transplants involving patients with Hermansky-Pudlak syndrome to date. Since individuals with this disease usually experience excessive bleeding and poor coagulation, bleeding during surgical procedures can be controlled with blood platelet transfusions.Since pulmonary fibrosis often occurs in individuals with Hermansky-Pudlak syndrome, the American Thoracic Society is a foundation that helps support people affected with this disease. Genetic testing for Hermansky-Pudlak syndrome can sometimes result in false negatives since not all of the genes of the disease have been identified.

Sources Used:- http://ghr.nlm.nih.gov/condition/hermansky-pudlak-syndrome - http://www.thoracic.org/patients/lung-disease-week/2013/rare-lung-disease/general-info2.php - http://facultylounge.whfreeman.com/files/images/figure_03_30_01.preview.jpg- http://www.intelligentdental.com/wp-content/uploads/2012/05/untitled19.png- http://www.ncbi.nlm.nih.gov/pubmed/10877819- https://rarediseases.org/rare-diseases/hermansky-pudlak-syndrome/


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