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Causes of Alström Syndrome

Alström syndrome is caused by mutations in the ALMS1 gene. Genes provide instructions for creating proteins that play a critical role in many functions of the body. When a mutation of a gene occurs, the protein product may be faulty, inefficient, or absent. Depending upon the functions of the particular protein, this can affect many organ systems of the body, including the brain.

In Alström syndrome, the gene mutation is inherited as an autosomal recessive trait. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.

Recessive genetic disorders occur when an individual inherits two copies of an abnormal gene for the same trait, one from each parent. If an individual inherits one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk for two carrier parents to both pass the altered gene and have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents is 25%. The risk is the same for males and females. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Investigators have determined that the ALMS1 gene is located on the short arm (p) of chromosome 2 (2p13). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 2q13” refers to band 13 on the long arm of chromosome 2. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

The ALMS1 gene contains instructions for creating (encoding) a specific protein known as ALMS1. The role and function of this protein in the body is not fully understood, but believed to be involved in ciliary function, cell cycle control and intracellular transport. The ALMS1 protein is expressed in all organ tissues of the body (ubiquitously expressed). Research is underway to determine this protein’s exact functions, which should greatly increase the understanding of Alström syndrome. Because symptoms of Alström syndrome vary greatly among family members, researchers suspect that additional genetic or environmental factors may play a role in the development and progression of Alström syndrome.

 

Signs and Symptoms-Alström Syndrome

 

Diagnosis of Alström Syndrome

Treating Alström Syndrome

 

 

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References:

rarediseases.org/rare-diseases/alstrom-syndrome/

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