For all the advances in medicine, a way to change the genes of a living person has not been discovered. As such, genetic syndromes generally have no cure. In some genetic disorders, effective treatments have been developed to ameliorate symptoms, allowing for a nearly normal life. The majority of genetic syndromes, however, have no effective treatments and supportive care helps provide best quality of life.
Down Syndrome
Down syndrome occurs in about one in every 800 births and is the most common genetic reason for intellectual disability. An individual with Down syndrome has three copies of chromosome 21 instead of the normal two. Occurring sporadically, a couple who has a child with Down syndrome has a low chance of a second affected child. The common features of Down syndrome are intellectual disability, characteristic facial features, heart defects and gastrointestinal malformations among others.
Cystic Fibrosis
Cystic fibrosis, or CF, is the most common, inherited genetic disorder in people from Northern European or Ashkenazi Jewish ancestry. Normally, each person has two copies of every gene. Cystic fibrosis is caused when a person has changes in both copies of the gene that causes CF---the CFTR gene. Parents of people with CF have a change in just one copy of CFTR and are therefore unaffected carriers. Nearly one in 25 individuals from Northern European or Jewish ancestry are carriers of CF. People of other ancestries have lower frequency of being carriers for CF. The most life-threatening complications of CF are lung infections and progressive lung disease. Other characteristics include poor growth, malnutrition from difficulty in utilizing vital nutrients in the diet and infertility in males.
Sickle Cell Disease
Sickle cell disease is a blood disorder that causes a certain molecule---hemoglobin, which carries oxygen though the body---to change shape when oxygen levels are low. The abnormally shaped molecules can get stuck in the very small blood vessels of the body causing pain, loss of red blood cells and anemia. "Thompson & Thompson: Genetics in Medicine" reports sickle cell disease occurs frequently in African Americans, equatorial Africans, Indians and people from the Mediterranean. An afflicted child inherits a defective beta-globin gene from each unaffected carrier parent.
Duchenne Muscular Dystrophy
Duchenne muscular dystrophy, or DMD, causes the muscles to weaken over time. The dystrophin gene that causes DMD is located on the X chromosome. Females who have a mutation in the dystrophin gene are generally unaffected, since they have a second X chromosome to compensate. Sons who inherit the abnormal dystrophin gene will have DMD, however, since they only have one X chromosome. Signs of DMD, such as trouble walking or an abnormal gait, are noticeable by the ages of 3 to 5. Most boys with DMD need to use a wheelchair by the age of 10 or 12. DMD is fatal, due to the weakening of the lung and cardiac muscles.
Huntington Disease
Huntington disease is an inherited genetic condition that develops in late adulthood. People with Huntington disease develop movement abnormalities, dementia and psychiatric manifestations. This syndrome is progressive, causing death about 15 to 18 years after onset of symptoms. Affected parents pass this syndrome on to their children---who have a 50 percent chance of inheriting the disease. According to GeneReviews, Huntington disease occurs once in every 14,000 to 33,000 individuals of Western European ancestry.
References
- "Thompson & Thompson Genetics in Metabolism (Seventh Edition)"; Robert Nessbaum; 2007
- Lancet; Down Syndrome; Nancy Roizen and David Patterson;2003
- GeneReviews: CFTR-Related Disorders
- GeneReveiws: Sickle Cell Disease
- GeneReviews: Dystrophinopathies
