Diabetes Mellitus Type 1 Inheritance

Type 1 diabetes is an inherited condition and individuals with a first degree relative who has the condition are at an increased risk of developing the condition. Details regarding the risk of inheriting type 1 diabetes are given below:

• In women with type 1 diabetes who have their baby before the age of 25, the risk of the child developing the condition is one in 25. If she has her baby after the age of 25, the risk falls to 1 in 100.
• If both parents have type 1 diabetes, the risk of the condition developing in offspring varies between 1 in 4 and 1 in 10. The risks are somewhat increased if one of the parents developed type 1 diabetes before the age of 11.
• Around 1 in 7 people with type 1 diabetes suffer from a condition called type 2 polyglandular autoimmune syndrome and these individuals have parathyroid and adrenal gland disorders in addition to type 1 diabetes. If one of the parents has type 2 polyglandular autoimmune syndrome, the risk that the child will inherit the condition, including type 1 diabetes, is 50%.

Genes associated with type 1 diabetes

Some genes have repeatedly been identified in people with type 1 diabetes. Among white individuals, examples of such genes include the HLA-DR3 or HLA-DR4 genes. Carrying these genes raises the risk that offspring will inherit type 1 diabetes. Children born with the HLADR3/4-DQ8 genotype make up nearly 50% of all children who develop type 1 diabetes before they are 5 years of age. Some studies on other ethnic groups have shown that similar risks are associated with the HLA-DR7 genotype among African Americans and with the HLA-DR9 gene among Japanese individuals.

Genetic studies have also located HLA class II genes at 6p21 and nearly 40 non-HLA genes that are closely associated with the inheritance of type 1 diabetes.