There are four types of Diabetes mellitus.


It is also called Insulin Dependent Diabetes (IDDM) or Juvenile Diabetes.

Although, it may occur at any age, but it usually develops in childhood or adolescence, before the age of 25. Equal incidences are seen in both sexes. But there are increased incidences in white population. This type of diabetes accounts for 10-15% of all cases of Diabetes mellitus. This type of Diabetes is acute in onset and progresses rapidly.

Type 1 Diabetes is caused by complete deficiency of Insulin resulting from Beta cell destruction. It can be explained on the basis of three basic factors:

(i) Genetic susceptibility:

  • A family history of Type 1 Diabetes mellitus is often found.
  • Moreover, it has been seen in identical turns, that if one twin has Type 1 diabetes, there is 50% chance of the second twin developing diabetes.
  • Majority of the cases of Type 1 diabetes has been seen in individuals with HLA-D Phenotypes (HLA-DR3 and HLA-DR4).

(ii) Auto Immunity:

  • The islet cell antibodies, sometimes instead of providing immunity to the pancreas, acts against it and destroys the insulin producing Beta cells of Pancreas. Thereby leading to raised glucose level and thus diabetes mellitus.
  • There may be Insulitis i.e. infiltration of lymphocytes around the Pancreatic islets further leading to loss of most of the Beta Cells.
  • Type 1 Diabetes may also be associated with other autoimmune diseases such as Hashimoto’s thyroiditis. Addison’s disease as pernicious anaemia.

(iii) Environmental Factors:

It may be:

  • Viral infections such as –congenital Rubella, Mumps, Measles and coxsackie B virus may lead to the onset of Type 1 Diabetes.
  • Exposure to cow’s milk rather then material milk in infancy may lead to development of type 1 DM. It is because the albumin from cow’s milk may react with islet cells of pancreas, leading to their destruction.
  • Geography also plays an important role, as the incidences of Type 1 DM are mainly high in Finland and Sardinia