Autoimmune diseases are diseases that are caused by the body's immune cells mistaking the normal cells of the body as foreign objects and therefore attacking them. Genetic diseases are those that occur because of defective genes, specific pieces of DNA that code for a specific trait, that are passed from parent to child. Because autoimmune diseases involve the immune system, they are complex diseases that require just the right combination of defective genes along with environmental triggers for the disease to occur.
Type I Diabetes
Type I diabetes, previously known as juvenile diabetes, is a disease caused by the body's inability to produce insulin. Insulin is a hormone produced in the pancreas that is necessary to help glucose (sugar) move from the blood into the cells where it can be used for energy. Without insulin, glucose remains in the blood and high concentrations of blood glucose can cause damage to organs throughout the body.
Type I diabetes, which accounts for only 5 to 10 percent of all diabetes cases, according to the American Diabetes Association, is usually diagnosed in children or young adults. Type I diabetes is not linked to a single gene, but several genetic factors must be inherited from both parents to have the predisposition for the disease. Environmental factors, which have yet to be determined, then trigger the onset of the disease.
Multiple Sclerosis
Multiple sclerosis (MS) is an autoimmune disease that causes inflammation of the central nervous system. It is caused by the cells of the immune system attacking the myelin, which is the fatty tissue that surrounds and protects the nerves. The myelin and nerves can be damaged, which interferes with the electrical impulses sent to and from the brain.
The exact mechanism of how MS occurs is not completely understood, but because MS clusters within families, it is known to have a genetic factor. It is not inherited by a single gene but by a specific combination of genes, as described by the Consortium of MS Centers. The Emory University School of Medicine reports that when both parents have MS, their offspring have a 30 percent chance of having the disease as well.
Crohn's Disease
Crohn's disease is a chronic disease that involves inflammation of the digestive system. The inflammation usually affects the intestinal walls, causing symptoms of chronic diarrhea, weight loss, abdominal pain, loss of appetite and fever. Crohn's disease, which affects approximately 1 million Americans, according to the Genetics Home Reference, is linked to an abnormality in chromosomes 5 and 10. Defects in genes on these chromosomes cause a person to be predisposed for Crohn's disease, which may then be triggered by environmental factors.
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is an autoimmune disease that affects approximately 1 million Americans, as reported by The National Institute of Arthritis and Musculoskeletal and Skin Diseases. RA involves the immune system attacking the cells lining the joints, known as the synovial cells, resulting in inflammation, stiffness, pain and loss of function in the joints. It is known that RA runs in families and scientists continue to study the role of genetics in the development of the disease. Research published by the Arthritis Foundation reveals that there are at least five genes that are linked to RA.
References
- American Diabetes Association: Type I
- Consortium of MS Centers: The Basics of Genetics in Multiple Sclerosis
- Genetic Home Reference: Crohn Disease
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Rheumatoid Arthritis
- Arthritis Foundation: The Genetics Behind Rheumatoid Arthritis
