Sunday, September 9, 2007

Diabetes Types - Other Types

Other Types

There are several rare causes of diabetes mellitus that do not fit into type 1, type 2, or gestational diabetes:

Genetic defects in beta cells (autosomal or mitochondrial)
Genetically-related insulin resistance, with or without lipodystrophy (abnormal body fat deposition)
Diseases of the pancreas (e.g. chronic pancreatitis, cystic fibrosis)
Hormonal defects
Chemicals or drugs
The tenth version of the International Statistical Classification of Diseases (ICD-10) contained a diagnostic entity named "malnutrition-related diabetes mellitus" (MRDM or MMDM, ICD-10 code E12). A subsequent WHO 1999 working group recommended that MRDM be deprecated, and proposed a new taxonomy for alternative forms of diabetes.[1] Classifications of non-type 1, non-type 2, non-gestational diabetes remains controversial.

Both type 1 and type 2 diabetes are at least partly inherited. Type 1 diabetes appears to be triggered by some (mainly viral) infections, or in a less common group, by stress or environmental exposure (such as exposure to certain chemicals or drugs). There is a genetic element in individual susceptibility to some of these triggers which has been traced to particular HLA genotypes (i.e., the genetic "self" identifiers relied upon by the immune system). However, even in those who have inherited the susceptibility, type 1 diabetes mellitus seems to require an environmental trigger. A small proportion of people with type 1 diabetes carry a mutated gene that causes maturity onset diabetes of the young (MODY).

Wolfram's syndrome - Wolfram's syndrome is an autosomal recessive neurodegenerative disorder that first becomes evident in childhood. It consists of diabetes insipidus, diabetes mellitus, optic atrophy, and deafness, hence the acronym DIDMOAD.

There is a stronger inheritance pattern for type 2 diabetes. Those with first-degree relatives with type 2 have a much higher risk of developing type 2, increasing with the number of those relatives. Concordance among monozygotic twins is close to 100%, and about 25% of those with the disease have a family history of diabetes. Candidate genes include KCNJ11 (potassium inwardly rectifying channel, subfamily J, member 11), which encodes the islet ATP-sensitive potassium channel Kir6.2, and TCF7L2 (transcription factor 7–like 2), which regulates proglucagon gene expression and thus the production of glucagon-like peptide-1.

Another risk factor is obesity, particularly central obesity (i.e., that in and around abdominal organs), which is found in approximately 85% of North American patients diagnosed with this type, so some experts believe that inheriting a tendency toward obesity also contributes.