Diabetes Type 3: Forms and Causes

What is type 3 diabetes?

The term diabetes type 3 refers to “other specific types of diabetes” and includes several special forms of diabetes mellitus. They are all much rarer than the two main forms, diabetes type 1 and diabetes type 2. Diabetes type 3 includes the following subgroups:

  • Diabetes type 3a: Caused by genetic defects in the insulin-producing beta cells; also called MODY
  • Diabetes type 3b: Caused by genetic defects in insulin action
  • Diabetes type 3d: Caused by diseases/disorders of the endocrine system
  • Diabetes type 3e: Caused by chemicals or drugs
  • Diabetes type 3f: Caused by viruses
  • Diabetes type 3g: Caused by autoimmune diseases
  • Diabetes type 3h: Caused by genetic syndromes

What is the life expectancy with type 3 diabetes?

If diabetes is genetic or caused by other diseases, it is usually the concomitant diseases that determine the course of diabetes.

Prognosis with MODY

The situation is quite different with MODY1: This form of type 3 diabetes is increasingly severe and often causes secondary diseases. Here, it is necessary to lower the elevated blood glucose levels with oral antidiabetics (sulfonylureas). Some MODY patients require insulin at an advanced age.

The other MODY variants are extremely rare.

MODY patients are often initially classified as type 1 diabetics. If they are severely overweight (which is rare), they are sometimes incorrectly diagnosed with type 2 diabetes.

What are the symptoms of type 3 diabetes?

Type 3a diabetes (MODY)

The mutations lead to abnormal development of the pancreas or islet cells (to which the beta cells belong) or to a disturbance in insulin secretion. In all of them – as in every form of diabetes – pathologically elevated blood glucose levels (hyperglycemia) occur.

The symptoms correspond to the typical signs in diabetes mellitus and are characterized by, among other things:

  • Severe thirst (polydipsia)
  • Increased urination (polyuria)
  • Itching (pruritus)
  • Unclear weight loss
  • Weakness in performance and concentration
  • Fatigue
  • Dizziness

Diabetes type 3b

This form of diabetes type 3 is based on genetic defects of insulin action. Different variants are distinguished:

Acanthosis nigricans is not specific to this form of type 3 diabetes. Rather, it is seen in many other diseases, for example gastric cancer.

In lipatrophic diabetes (Lawrence syndrome), insulin resistance is very pronounced. In addition, those affected gradually lose body fat – they lose a lot of body weight. This is indicated by the term lipatrophy (= loss of subcutaneous fatty tissue).

Diabetes type 3c

  • Chronic inflammation of the pancreas (chronic pancreatitis): it affects both the secretion of digestive enzymes (exocrine pancreatic function) and the secretion of insulin, glucagon and other pancreatic hormones (endocrine function). The main cause is chronic alcohol consumption.
  • Injuries to the pancreas(such as accidents)
  • Surgical removal of the pancreas (as a whole or in parts), for example due to a tumor
  • Cystic fibrosis: incurable hereditary disease. About 30 percent of patients also develop type 3 diabetes because viscous secretions form in the pancreas. It clogs the excretory ducts and damages the cells that produce insulin and other pancreatic hormones. Insulin therapy is therefore always necessary.

Diabetes type 3d

Diabetes type 3 sometimes occurs in the context of other hormonal (endocrine) diseases and disorders. They are then grouped under the term diabetes type 3d. The triggering hormonal diseases include:

  • Cushing’s disease: Here, the body releases more of the hormone ACTH, which in turn increases the release of the body’s own cortisone. This causes increased blood sugar levels. Other consequences of ACTH excess include truncal obesity, osteoporosis and high blood pressure.
  • Somatostatinoma: Malignant tumor of the pancreas or duodenum that produces increased amounts of the hormone somatostatin. Among other things, this inhibits insulin production. As a result, blood sugar can no longer be lowered sufficiently.
  • Pheochromocytoma: Usually benign tumor of the adrenal medulla. For example, it stimulates the formation of new glucose (gluconeogenesis) to such an extent that blood glucose levels rise abnormally.
  • Hyperthyroidism: Hyperthyroidism also sometimes derails blood glucose levels.

Diabetes type 3e

Various chemicals and (rarely) medications cause type 3e diabetes. These include, for example:

  • Pyrinuron: rodent poison (rodenticide) and component of the rat poison Vacor (was only on the market in the U.S. and is now no longer approved)
  • Pentamidine: active ingredient against protozoa; used in the treatment of parasitic diseases such as leishmaniasis
  • Thyroid hormones: For the treatment of hypothyroidism.
  • Thiazide diuretics: Diuretics used to treat conditions such as heart failure and high blood pressure.
  • Phenytoin: Anticonvulsant used to treat epilepsy and cardiac arrhythmias
  • Beta-sympathomimetics: Used to treat COPD, asthma and irritable bladder, among other conditions
  • Diazoxide: For the treatment of low blood sugar (hypoglycemia)
  • Nicotinic acid: Water-soluble vitamin from the group of B vitamins; worsens glucose tolerance (i.e. the body’s healthy response to glucose intake)

Diabetes type 3f

In rare cases, certain viral infections trigger type 3 diabetes, such as rubella virus and cytomegalovirus. Unborn children are primarily at risk: in these cases, the expectant mother transmits the viruses to them. Possible viral triggers of type 3 diabetes include:

  • Congenital cytomegalovirus infection: The cytomegalovirus (CMV) belongs to the group of herpes viruses and is very common worldwide. For healthy adults, it is usually harmless. For unborn children, however, a CMV infection can sometimes cause serious health problems and pose a threat to life. Among other things, the child develops pancreatic inflammation.

Diabetes type 3g

In individual cases, certain autoimmune diseases result in type 3 diabetes:

  • Anti-insulin receptor antibodies: They occupy the docking sites for insulin on the surface of body cells. Insulin is prevented from docking and therefore no longer ensures that blood sugar is absorbed into the cells.

Diabetes type 3h

This includes forms of type 3 diabetes that occur in association with various genetic syndromes. These include:

  • Trisomy 21 (Down syndrome): Affected individuals have three copies of chromosome 21 instead of two.
  • Turner syndrome: In affected girls/women, one of the two X chromosomes is missing or structurally defective.
  • Wolfram syndrome: Neurodegenerative disease associated with neurological symptoms, optic nerve atrophy, type 1 diabetes mellitus and diabetes insipidus. The latter is a disorder of water balance that is not diabetes mellitus.
  • Porphyria: Hereditary or acquired metabolic disease in which the formation of the red blood pigment (heme) is disturbed.
  • Friedreich’s ataxia: Hereditary disease of the central nervous system causing, among other things, neurological deficits, skeletal malformations and diabetes.
  • Dystrophia myotonica: Inherited muscle disease with muscle atrophy and weakness as well as other complaints such as cardiac arrhythmias, cataracts and diabetes mellitus.

Read more about the typical symptoms of diabetes in the article Diabetes mellitus.