Type I Diabetes
Type I diabetes is also known as insulin-dependent diabetes. Type I diabetes typically affects patients early in their lives, either in childhood or when they are young adults, although it can start later in life. Type I diabetes is caused by problems in the immune system. It is thought to be a result of a combination of inherited (genetic) factors as well as another trigger, such as an infection or diet. The human genome has eighteen different regions (which have been termed IDDM 1-18 by geneticists) that have been linked to the development of Type I diabetes. Many of these regions are known to have genes that relate to the immune system and could cause the abnormal immune activation that causes Type I diabetes.
Type II Diabetes
Type II diabetes is often called adult-onset diabetes because it typically occurs later in life. This form of diabetes is also thought to have a genetic component. However, unlike other forms of diabetes which can be linked to discrete portion of the genome, Type II diabetes is thought to be a result of a combination of genetic factors which aren't completely understood. Researchers are currently looking at the entire genomes of families with Type II diabetes in an attempt to identify the genetic factors. Currently the only two genes which have been identified are called CAPN10 and HNF4A. Patients who have these genes are thus at a higher risk of developing Type II diabetes.
Other Forms
Although most cases of diabetes can be termed either Type I or II and are caused by multiple genetic mutations, there are some rare cases that are caused by single genes. One such rare form is called maturity onset diabetes in the young and is linked to single mutations in various genes (including HNF4A as well as genes that relate to insulin), which leads to different subtypes of this rare kind of diabetes. Other rare forms of diabetes are caused by mutations in the DNA that encodes mitochondria. This form of diabetes is often linked with deafness.
