UNDERSTANDING GENETIC DISEASES

Impact of Genetic Diseases

Genetic diseases impact people from all over the world, for the entirety of their lifetime. Due in part to extensive research and the dedication of patients, scientists, and communities, some genetic diseases can now be treated by approved gene therapies. As time goes on, research is aiming to develop even more therapies for a broader range of genetic diseases.
How common are genetic diseases?
Types of Treatment for Genetic Diseases
How common are genetic diseases?
Types of Treatment for Genetic Diseases

How common are genetic diseases?
There are an estimated 10,000 different types of single-gene diseases (also called monogenic diseases), which are diseases caused by mutations in a single gene. The World Health Organization estimates that 10 out of every 1000 people are affected.1 This means that between 70 million and 80 million people in the world are living with one of these diseases.

There are an estimated 10,000 different types of Single-gene diseasestypes of diseases, also called monogenic diseases, in which a mutation is present in one gene only

See glossary for more terms > (also called monogenic diseases), which are diseases caused by mutations in a single gene. The World Health Organization estimates that 10 out of every 1000 people are affected.1 This means that between 70 million and 80 million people in the world are living with one of these diseases.1,2

Even with that many people affected, individual single-gene diseases are considered rare. Below are examples of single-gene diseases and their rates of occurrence.
EXAMPLES OF SINGLE-GENE DISEASES AND RATES OF OCCURRENCE
Single-gene diseases Rate of occurrence
Achondroplasia is a bone growth disorder that causes short-limbed dwarfism in which there is a problem converting cartilage into bone3
 1 in 15,000 to 40,000 births
Beta-thalassemia is a blood disorder that reduces production of hemoglobin and causes anemia, bone, and organ damage4
 Most prevalent in people from, or with ancestors from, Mediterranean countries, North Africa, Middle East, India, Central Asia, and Southeast Asia
Cystic fibrosis is an inherited disease characterized by a buildup of thick, sticky mucus that causes respiratory and digestive problems5
 1 in 2500 to 3500 White Americans
1 in 17,000 African Americans 
1 in 31,000 Asian Americans
Fragile X syndrome is a condition that causes a range of developmental problems including cognitive impairment and learning disabilities6
 1 in 4000 males
1 in 8000 females
Huntington disease is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of cognitive ability7
 3 to 7 per 100,000 people of European descent

Less common in people of Japanese, Chinese, and African descent
Sickle cell disease (SCD) is a progressive genetic disease characterized by blood vessel damage and blocked blood vessels. In SCD, high levels of abnormal sickle hemoglobin in red blood cells lead to unpredictable and life-threatening complications and chronic organ damage, including organ failure8,9
 Although SCD can and does affect people of all races, it is often perceived as a Black disease in the US.

SCD affects over 100,000 people in the US including:
  • ~1 in 365 newborn African Americans
  • ~1 in 16,300 newborn Hispanic Americans
  • ~1 in 25,800 Asian/Pacific Islanders
  • ~1 of 41,600 non-Hispanic/White
  • Affects men and women equally
Hemophilia is a an inherited bleeding disorder where blood fails to clot properly. Problems with hemophilia can range from spontaneous bleeds in joints, muscles, and organs as well as prolonged bleeding following surgery. The bleeding is caused by a missing protein. Depending on the missing protein, a person may have either hemophilia A or B.10 Hemophilia primarily affects males with over 30,000 men in the US currently living with the disease.11

1 in 5,617 male births have hemophilia A
1 in 19,283 male births have hemophilia B             
Keep in mind that the examples listed here are not an exhaustive list of diseases and rates of occurrence. Please refer to the RESOURCES section to find more disease-specific information through links to additional organizations.

Types of Treatment for Genetic Diseases

Symptomatic treatment

hemophilia
Relieving symptoms is one of the ways that treating a genetic disease can potentially improve patient outcomes.12 For example, people with Hemophiliaan inherited disease where blood does not clot properly

See glossary for more terms > may need a treatment that replaces the clotting factor that their bodies fail to produce.

Solid organ transplant

For genetic diseases that only affect one organ in the body, solid organ transplantation may be an option.13 Removing a diseased organ and replacing it with a donor organ can help prevent disease complication and may help improve life expectancy. Solid organ transplant, as a potential curative option, can occur in the following diseases:

  • Metabolic liver disease
  • Polycystic kidney disease
  • Congenital heart disease
When considering treatment options like solid organ transplantation, people should discuss their specific situation and the risks and benefits with their doctor.14,15

 

Bone marrow transplant (BMT) stem cell transplant hematopoietic stem cell transplant (HSCT) Allogeneic BMT Autologous BMT

About 65 years ago, another approach for treating certain genetic diseases became available: Bone marrow transplant (BMT)the process of infusing blood stem cells from another person (a donor) in a person who has a genetic disease or whose bone marrow or immune system is compromised to help correct or restore normal cell function

See glossary for more terms >. This treatment is also called stem cell transplant or hematopoietic stem cell transplant (HSCT).16

Bone marrow transplants for genetic diseases treat the disease at the genetic level with the goal of providing a cure to the diseases. In these types of procedures, healthy Blood (or hematopoietic) stem cellscells found in the bone marrow and circulating blood that develop into different types of blood cells, such as red blood cells, white blood cells, and platelets

See glossary for more terms > from a donor, which have a functional gene, are transplanted into a person with a genetic disorder. The goal is for the functional gene in the donor cells to compensate for the mutated gene that causes genetic disease. The functional gene allows the missing, defective, or overproduced protein to be made, or made in amounts that have a therapeutic effect on the person.17-19

Stem cells are transplanted into a patient because they have the ability to form many other types of cells in the body.19,20 Blood stem cells are predominantly found in the bone marrow. As they grow (mature), they can eventually become many blood cells, including21:

There are two types of BMT:

  • Allogenic hematopoietic stem cell transplant (allogenic HSCT or allo HSCT)a transplant in which the person receives blood stem cells or bone marrow cells from another person (a donor)

    See glossary for more terms >     for genetic diseases uses cells from another person, or a Donorin a hematopoietic stem cell transplant, the person who donates their blood stem cells

    See glossary for more terms >    , who does not have the disease. The donor’s healthy cells have a functional gene that is transplanted into the person’s body. In allogeneic BMTs, the donor and patient cells should be as close to a match as possible. If they aren’t, there is a chance that the patient’s immune system will recognize the donor cells as foreign and reject them, causing Graft rejectiona situation that occurs when donated bone marrow is infused and then rejected by the person receiving the donation

    See glossary for more terms >    .17

    The opposite can also happen, in which the donor cells attack the host; this is called Graft-versus-host diseasean adverse reaction to a bone marrow transplant in which the body attacks its own cells

    See glossary for more terms >     (GVHD). Donor blood stem cells that most closely resemble the person being treated may be found among siblings. However, matches may also be found among the general population.17,22,23 Allogeneic BMT may have limited feasibility as a treatment due to a person’s age, overall health, and donor match availability.24,25

  • Autologous hematopoietic stem cell transplant (autologous HSCT or auto HSCT)a transplant in which the patient receives their own blood stem cells or bone marrow that was previously collected

    See glossary for more terms >     is a similar treatment to allogeneic BMT but uses a person’s own cells for the transplant, so no donor is required. Because the blood stem cells come from the person, there is a lesser chance that their own immune system will reject them (or vice versa); however, this type of BMT is not beneficial for a patient with a genetic disease.17,18

Image of allogeneic bone marrow transplant
Image of autologous bone marrow transplant

While BMTs have the potential to treat disease at the genetic level, they also come with serious risks. These include stem cell (graft) failure or complications, organ damage, infection, infertility, cancers that arise due to treatment (also called secondary cancers), and death. Some of these risks may be due to the chemotherapy that is required before a bone marrow transplant. This type of chemotherapy ensures that any diseased cells and malfunctioning bone marrow are cleared out to make room for the functioning, transplanted donor stem cells.26

Gene therapy

Thanks to continuous technological refinements and advancements over the past 30 years, Gene therapya method of treating genetic diseases at the genetic level (the source) with the goal of changing the course of a disease

See glossary for more terms > has become a potential treatment option for more people who are living with genetic diseases.27 Gene therapy is what genehome is all about. As you explore, you will have the opportunity to learn much more about the many aspects of gene therapy throughout genehome.

Continue building your knowledge by learning about the BASICS OF GENE THERAPY.
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Curious how gene therapy has evolved?
See Gene Therapy History
Explore genehome
Curious how gene therapy has evolved?
See Gene Therapy History
Other topics you may be interested in:

Examples of Approved Gene Therapies

Types of Gene Therapy

Basics of Gene Therapy

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References

1. World Health Organization. Genes and human diseases. Accessed July 1, 2021. https://www.who.int/genomics/public/geneticdiseases/en/index2.html 2. Worldometer. Current world population. Accessed July 1, 2021. https://www.worldometers.info/world-population/ 3. National Institutes of Health. Genetics Home Reference. Achondroplasia. Accessed July 1, 2021. https://ghr.nlm.nih.gov/condition/achondroplasia#statistics 4. National Institutes of Health. Genetics Home Reference. Beta thalassemia. Accessed July 1, 2021. https://ghr.nlm.nih.gov/condition/beta-thalassemia#statistics 5. National Institutes of Health. Genetics Home Reference. Cystic fibrosis. Accessed July 1, 2021. https://ghr.nlm.nih.gov/condition/cystic-fibrosis#statistics 6. National Institutes of Health. Genetics Home Reference. Fragile x syndrome. Accessed July 1, 2021. https://ghr.nlm.nih.gov/condition/fragile-x-syndrome#statistics 7. National Institutes of Health. Genetics Home Reference. Huntington disease. Accessed July 1, 2021. https://ghr.nlm.nih.gov/condition/huntington-disease#statistics 8. National Institutes of Health. Genetics Home Reference. Sickle cell disease. Accessed July 1, 2021. https://ghr.nlm.nih.gov/condition/sickle-cell-disease#statistics. 9. Centers for Disease Control and Prevention. Sickle Cell Disease. Accessed April 26, 2021. https://www.cdc.gov/ncbddd/sicklecell/data.html. 10. Centers for Disease Control and Prevention. What is hemophilia? Accessed July 1, 2021. https://www.cdc.gov/ncbdddlhemophilialfacts.html 11. Soucie JM, Miller CH, Dupervil B, Le B, Buckner TW. Occurrence rates of haemophilia among males in the United States based on surveillance conducted in specialized haemophilia treatment centres. Haemophilia. 2020;26(3):487-493. 12. National Institutes of Health. Genetics Home Reference. Help me understand genetics. Accessed July 1, 2021. https://ghr.nlm.nih.govlprimer. 13. Kim JS, Kim KM, Oh SH, et al. Liver transplantation for metabolic liver disease: experience at a living donor dominant liver transplantation center. Pediatr Gastroenterol Hepatol Nutr. 2015;18(1):48-54. 14. Moscalu R, Smith AM, Sharma HL. Diseases that can be cured only by organ donations. Arch Clin Cases. 2015;2(4):182-197. 15. Moore T. Medscape. Bone marrow transplantation. Accessed July 1, 2021. https://emedicine.medscape.com/article/1014514-overview 16. Johns Hopkins Medicine. Bone marrow transplantation. Accessed July 1, 2021. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-marrow-transplantation 17. Aiuti A, Scala S, Chabannon C. Biological properties of HSC: scientific basis for HSCT. In: Carreras E, Dufour C, Mohty M, Kroger N, eds. The EBMT Handbook: Hematopoietic Stem Cell Transplantation and Cellular Therapies [Internet]. 7th edition. Cham (CH): Springer; 2019. Accessed July 1, 2021. https://www.ncbi.nlm.nih.gov/books/NBK553952/ 18. Naldini L. Genetic engineering of hematopoiesis: current stage of clinical translation and future perspectives. EMBO Mol Med. 2019;11(3):e9958. 19. Morgan RA, Gray D, Lomova A, Kohn D. Hematopoietic stem cell gene therapy: progress and lessons learned. Cell Stem Cell. 2017;21(5):574-590. 20. National Institutes of Health. National Cancer Institute. Blood-forming stem cell transplants. Accessed July 1, 2021. https://www.cancer.gov/about-cancer/treatment/types/stem-cell-transplant/stem-cell-fact-sheet#what-are-bone-marrow-and-hematopoietic-stem-cells. 21. Mattsson J, Ringdén O, Storb R. Graft failure after hematopoietic cell transplantation. Biol Blood Marrow Transplant. 2008;14(suppl 1):165-170. 22. American Cancer Society. Types of stem cell transplants for cancer treatment. Accessed July 1, 2021. https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/stem-cell-transplant/types-of-transplants.html 23. Be the Match. Donating bone marrow donation frequently asked questions. Accessed July 1, 2021. https://bethematch.org/support-the-cause/donate-bone-marrow/donation-faqs/ 24. Be the Match. Bone marrow donation medical guidelines. Accessed July 1, 2021. https://bethematch.org/support-the-cause/donate-bone-marrow/possible-match/medical-guidelines-when-you-match-a-patient/ 25. Mayo Clinic. Bone marrow transplant. Accessed July 1, 2021. https://www.mayoclinic.org/tests-procedures/bone-marrow-transplant/about/pac-20384854 26. Wirth T, Parker N, Yla-Herttuala. History of gene therapy. Gene. 2013;525:162-169.

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