What gene changes cause Alstrom syndrome?
Alstrom syndrome is caused by changes, also called variants, in the ALMS1 gene. Every person has about 20,000-25,000 genes in their cells that contain our body's genetic information. These genes are composed of DNA. Our genes are inherited from our parents and passed on to our children. Genes are like our body's instruction manual - they control the growth, development and enable the normal function of the body. Genes produce specific proteins that the body needs to grow and work properly. When there is an unexpected change, also called a variant, in a gene, the protein that the gene produces may be absent, not work properly, or be overproduced. The ALMS1 gene produces a protein that hasn't been named yet. The exact function of this protein is not yet understood but it is found in all tissues of the body. People with Alstrom syndrome have changes in both copies of their ALMS1 gene. Because of these changes in the ALMS1 gene, it most likely produces a nonfunctional version of this protein.
To find a medical professional nearby who can discuss information about gene changes in Alstrom syndrome, the National Society of Genetic Counselors website offers a Find a Genetic Counselor tool on its website. This can help people find a genetic counselor within the United States. The MedlinePlus Genetics website has information on the ALMS1 gene.
- Alstrom syndrome. The National Organization for Rare Disorders website. Accessed May 4, 2018. https://rarediseases.org/rare-diseases/alstrom-syndrome/
- MedlinePlus Genetics. (2021, February). Alstrom Syndrome. Accessed on Feb 24, 2021 from https://medlineplus.gov/genetics/condition/alstrom-syndrome/
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Why does Alstrom syndrome cause so many different symptoms?
Researchers have demonstrated that Alstrom syndrome is a ciliopathy. Cilia are tiny, hair-like structures located on virtually all the cells of the body. Alstrom syndrome is caused by changes, also called variants in the ALMS1 gene. This gene produces a protein and at this point in time, researchers do not completely understand what this protein does. However, they believe that this protein plays a vital role in the health, function and development of cilia, or structures nearby or related to cilia. Because cilia are found on almost all cell types this might explain why Alstrom syndrome affects so many different organ systems of the body.
There is research indicating that the ALMS gene and its protein are involved in the melanocortin-4 receptor pathway. This metabolic pathway is involved in several rare disorders of obesity syndromes including Alstrom syndrome. The melanocortin-4 receptor is responsible for providing the signal that tells your brain that you are full and it's time to stop eating. When the pathway is interrupted, like a broken traffic signal, the signal telling you that you are full never arrives. This involvement of the ALMS1 gene in this pathway could be the reason individuals with Alstrom syndrome gain weight and become obese.
The Ciliopathy Alliance is a nonprofit charity that has more information about cilia and ciliopathies (disorders caused by problems with cilia).
- Alstrom syndrome. The National Organization for Rare Disorders website. Accessed February 23, 2021. https://rarediseases.org/rare-diseases/alstrom-syndrome/
- Marshall, JD et. al. (2012, May). Gene Reviews. Alstrom Syndrome. Retrieved on June 4, 2018 from https://www.ncbi.nlm.nih.gov/books/NBK1267/
Does everyone with Alstrom syndrome have a gene mutation?
Alstrom syndrome is caused by changes (also called variants) in the ALMS1 gene. Everyone has two copies of the ALMS1 gene. They inherit one from their father and one from their mother. In people with Alstrom syndrome, both copies of their ALMS1 genes have disease-causing changes. Alstrom syndrome has what is called an autosomal recessive inheritance. This means that someone with Alstrom syndrome has changes to both of their ALMS1 genes to develop this disorder. Usually, each of their parents has a gene change in one of their ALMS1 and no change in the other copy of their ALMS1 gene. Each parent is a carrier. Carriers do not develop symptoms of the disorder. People with Alstom syndrome inherit the changed copies of ALMS1 from each of their parents.
If two carriers for Alstrom syndrome have children together, they have a 1 in 4 (or 25%) chance to have a child with Alstrom syndrome. They have a 1 in 2 (or 50%) chance to have a child that is a carrier, just like them. They also have a 1 in 4 (or 25%) chance to have a child that is not a carrier and does not have Alstrom syndrome. These odds are the same in every pregnancy that the carriers have together. No parent has control over which genes they pass, or do not pass, to their children.
People with Alstrom syndrome may be the first in their family to be diagnosed with this condition or they may have siblings with it. Because their parents only have one altered ALMS1 gene each but do not have Alstrom syndrome, this gene change can be inherited in a family without anyone being aware that it is in their DNA. However, when they have a child with someone who also has a gene change in their ALMS1 gene, they can have a child with Alstrom syndrome. This inherited disorder seems to pop up out of the blue. Unless they have a child with another person with Alstrom syndrome, people with this disorder are unlikely to have a child with this condition.
- Marshall, JD et. al. (2019, June). GeneReviews. Alstrom Syndrome. Retrieved on February 23, 2021 from https://www.ncbi.nlm.nih.gov/books/NBK1267/
- MedlinePlus Genetics. (2021, February). Alstrom Syndrome. Accessed on February 23, 2021 from https://medlineplus.gov/genetics/condition/alstrom-syndrome/