Permanent neonatal diabetes mellitus is a type of diabetes that first appears within the first 6 months of life and persists throughout the lifespan. This form of diabetes is characterized by high blood sugar levels (hyperglycemia) resulting from a shortage of the hormone insulin. Insulin controls how much glucose (a type of sugar) is passed from the blood into cells for conversion to energy.

Individuals with permanent neonatal diabetes mellitus experience slow growth before birth (intrauterine growth retardation). Affected infants have hyperglycemia and an excessive loss of fluids (dehydration) and are unable to gain weight and grow at the expected rate (failure to thrive).

In some cases, people with permanent neonatal diabetes mellitus also have certain neurological problems, including developmental delay and recurrent seizures (epilepsy). This combination of developmental delay, epilepsy, and neonatal diabetes is called DEND syndrome. Intermediate DEND syndrome is a similar combination but with milder developmental delay and without epilepsy.

A small number of individuals with permanent neonatal diabetes mellitus have an underdeveloped pancreas. Because the pancreas produces digestive enzymes as well as secreting insulin and other hormones, affected individuals experience digestive problems such as fatty stools and an inability to absorb fat-soluble vitamins.

Permanent neonatal diabetes mellitus may be caused by mutations in several genes.

About 30 percent of individuals with permanent neonatal diabetes mellitus have mutations in the KCNJ11 gene. An additional 20 percent of people with permanent neonatal diabetes mellitus have mutations in the ABCC8 gene. These genes provide instructions for making parts (subunits) of the ATP-sensitive potassium (K-ATP) channel. Each K-ATP channel consists of eight subunits, four produced from the KCNJ11 gene and four from the ABCC8 gene.

K-ATP channels are found across cell membranes in the insulin-secreting beta cells of the pancreas. These channels open and close in response to the amount of glucose in the bloodstream. Closure of the channels in response to increased glucose triggers the release of insulin out of beta cells and into the bloodstream, which helps control blood glucose levels.

Mutations in the KCNJ11 or ABCC8 gene that cause permanent neonatal diabetes mellitus result in K-ATP channels that do not close, leading to reduced insulin secretion from beta cells and impaired blood glucose control.

Mutations in the INS gene, which provides instructions for making insulin, have been identified in about 20 percent of individuals with permanent neonatal diabetes mellitus. Insulin is produced in a precursor form called proinsulin, which consists of a single chain of protein building blocks (amino acids). The proinsulin chain is cut (cleaved) to form individual pieces called the A and B chains, which are joined together by connections called disulfide bonds to form insulin. Mutations in the INS gene are believed to disrupt the cleavage of the proinsulin chain or the binding of the A and B chains to form insulin, leading to impaired blood glucose control.

Permanent neonatal diabetes mellitus can also be caused by mutations in other genes, some of which have not been identified.

Normal Function

The ABCC8 gene provides instructions for making the sulfonylurea receptor 1 (SUR1) protein. The SUR1 protein is one part (subunit) of the ATP-sensitive potassium (K-ATP) channel that is found across cell membranes in the beta cells of the pancreas. Beta cells secrete insulin, which is a hormone that helps control blood sugar levels. Insulin controls how much sugar (in the form of glucose) is passed from the bloodstream into cells to be used as energy. The K-ATP channel controls the secretion of insulin out of beta cells and into the bloodstream. These channels open and close in response to the amount of glucose in the bloodstream, which helps regulate insulin secretion and control blood glucose levels. The closing of the channels results in a process that triggers insulin secretion by beta cells.

Health Conditions Related to Genetic Changes

Congenital hyperinsulinism

More than 300 mutations in the ABCC8 gene have been found to cause congenital hyperinsulinism. This condition causes frequent episodes of low blood glucose (hypoglycemia), decreased energy, and irritability. Most of these mutations change single protein building blocks (amino acids) in the SUR1 protein.

Some ABCC8 mutations prevent the SUR1 protein from reaching the cell membrane, interfering with the proper formation of the K-ATP channel. Other mutations interfere with the K-ATP channel's function or its responses to outside molecules. Defective K-ATP channels lead to the constant release of insulin from beta cells. As a result, glucose is rapidly removed from the bloodstream. Without treatment, the hypoglycemia caused by congenital hyperinsulinism may result in serious complications such as intellectual disability and seizures.

Permanent neonatal diabetes mellitus

At least 14 mutations in the ABCC8 gene have been identified in people with permanent neonatal diabetes mellitus. Individuals with this condition often have a low birth weight and develop increased blood sugar (hyperglycemia) within the first 6 months of life.

ABCC8 gene mutations that cause permanent neonatal diabetes mellitus change single amino acids in the protein sequence. These mutations result in K-ATP channels that do not close, leading to reduced insulin secretion from beta cells and impaired blood sugar control.

Maturity-onset diabetes of the young

MedlinePlus Genetics provides information about Maturity-onset diabetes of the young

Other disorders

Other ABCC8 gene mutations that have a relatively mild effect on K-ATP channel function as compared to that seen in permanent neonatal diabetes mellitus (see above) cause a condition called transient neonatal diabetes mellitus. Infants with this condition have hyperglycemia during the first 6 months of life, but their blood sugar returns to normal by age 18 months. However, affected individuals usually develop hyperglycemia again during adolescence or early adulthood. As in permanent neonatal diabetes mellitus, ABCC8 gene mutations that cause transient neonatal diabetes mellitus interfere with K-ATP channel closure and lead to a reduction in insulin secretion.

Some studies suggest that normal variations (polymorphisms) in the ABCC8 gene are associated with an increased risk of type 2 diabetes, the most common form of diabetes. Other studies, however, have not found an association between ABCC8 gene variants and type 2 diabetes. People with this disease have hyperglycemia because the body does not respond correctly to the insulin secreted from beta cells. Although changes in the ABCC8 gene may be associated with type 2 diabetes, a combination of lifestyle, genetic, and environmental factors all play a part in determining the risk of this complex disorder.

Other Names for This Gene

• ABC36
• ABCC8_HUMAN
• ATP-binding cassette, sub-family C (CFTR/MRP), member 8
• ATP-binding cassette, sub-family C, member 8
• MRP8
• SUR
• SUR1
• TNDM2

Genomic Location

Normal Function

The INS gene provides instructions for producing the hormone insulin, which is necessary for the control of glucose levels in the blood. Glucose is a simple sugar and the primary energy source for most cells in the body.

Insulin is produced in a precursor form called proinsulin, which consists of a single chain of protein building blocks (amino acids). The proinsulin chain is cut (cleaved) to form individual pieces called the A and B chains, which are joined together by connections called disulfide bonds to form insulin.

Health Conditions Related to Genetic Changes

Permanent neonatal diabetes mellitus

At least 10 mutations in the INS gene have been identified in people with permanent neonatal diabetes mellitus. Individuals with this condition often have a low birth weight and develop increased blood glucose (hyperglycemia) within the first 6 months of life.

INS gene mutations that cause permanent neonatal diabetes mellitus change single protein building blocks (amino acids) in the protein sequence. These mutations are believed to disrupt the cleavage of the proinsulin chain or the binding of the A and B chains to form insulin, leading to impaired blood glucose control.

Maturity-onset diabetes of the young

MedlinePlus Genetics provides information about Maturity-onset diabetes of the young

Type 1 diabetes

MedlinePlus Genetics provides information about Type 1 diabetes

Other disorders

Mutations in the INS gene can also cause other disorders involving insulin production and blood glucose control. Some individuals with INS gene mutations have increased levels of proinsulin in their blood (hyperproinsulinemia) and may also have impaired blood glucose control. INS gene mutations are also associated with a disorder called maturity-onset diabetes of the young (MODY). This term refers to hereditary forms of relatively mild diabetes mellitus caused by changes in single genes.

Other Names for This Gene

• IDDM2
• ILPR
• INS_HUMAN
• insulin preproprotein
• IRDN
• MODY10
• proinsulin

Genomic Location

Normal Function

The KCNJ11 gene provides instructions for making parts (subunits) of the ATP-sensitive potassium (K-ATP) channel. Each K-ATP channel consists of eight subunits. Four subunits are produced from the KCNJ11 gene, and four are produced from another gene called ABCC8.

K-ATP channels are found in beta cells, which are cells in the pancreas that secrete the hormone insulin. The K-ATP channels are embedded in cell membranes, where they open and close in response to the amount of glucose in the bloodstream. Glucose is a simple sugar and the primary energy source for most cells in the body. Closure of the K-ATP channels in response to increased glucose triggers the release of insulin out of beta cells and into the bloodstream, which helps control blood glucose levels.

Health Conditions Related to Genetic Changes

Congenital hyperinsulinism

More than 30 mutations in the KCNJ11 gene have been found to cause congenital hyperinsulinism. This condition causes frequent episodes of low blood glucose (hypoglycemia), decreased energy, and irritability. Most of these mutations change single protein building blocks (amino acids) in the protein sequence, reducing or preventing activity of the K-ATP channels. Loss of K-ATP channel function leads to the constant release of insulin from beta cells. As a result, glucose is rapidly removed from the bloodstream. Without treatment, the hypoglycemia caused by congenital hyperinsulinism may result in serious complications such as intellectual disability and seizures.

Permanent neonatal diabetes mellitus

At least 30 mutations in the KCNJ11 gene have been identified in people with permanent neonatal diabetes mellitus. Individuals with this condition often have a low birth weight and develop increased blood glucose (hyperglycemia) within the first 6 months of life.

KCNJ11 gene mutations that cause permanent neonatal diabetes mellitus change single amino acids in the protein sequence. These mutations result in K-ATP channels that do not close, leading to reduced insulin secretion from beta cells and impaired blood glucose control.

Gestational diabetes

MedlinePlus Genetics provides information about Gestational diabetes

Maturity-onset diabetes of the young

MedlinePlus Genetics provides information about Maturity-onset diabetes of the young

Other disorders

Other KCNJ11 gene mutations that have a relatively mild effect on K-ATP channel function as compared to that seen in permanent neonatal diabetes mellitus (see above) cause a condition called transient neonatal diabetes mellitus. Infants with this condition have hyperglycemia during the first 6 months of life, but their blood glucose returns to normal by age 18 months. However, affected individuals usually develop hyperglycemia again during adolescence or early adulthood. As in permanent neonatal diabetes mellitus, KCNJ11 gene mutations that cause transient neonatal diabetes mellitus also interfere with K-ATP channel closure and lead to a reduction in insulin secretion.

A normal variation (polymorphism) in the KCNJ11 gene is associated with an increased risk of type 2 diabetes, the most common form of diabetes. This variant leads to a change in the K-ATP channel, replacing the amino acid glutamic acid with the amino acid lysine at position 23, written as Glu23Lys or E23K. People with type 2 diabetes have hyperglycemia because the body does not respond correctly to the insulin secreted from beta cells. The same variant has also been associated with changes in the heart's response to stress, leading to an increased risk of heart failure. Although changes in the KCNJ11 gene can be associated with type 2 diabetes and heart failure, a combination of lifestyle, genetic, and environmental factors all play a part in determining the risk of these complex disorders.

Other Names for This Gene

• ATP-sensitive inward rectifier potassium channel 11
• beta-cell inward rectifier subunit
• BIR
• HHF2
• IKATP
• inward rectifier K(+) channel Kir6.2
• inwardly rectifying potassium channel KIR6.2
• KIR6.2
• MGC133230
• potassium channel, inwardly rectifying subfamily J member 11
• potassium channel, inwardly rectifying subfamily J, member 11
• potassium inwardly-rectifying channel, subfamily J, member 11
• TNDM3

Genomic Location

Permanent neonatal diabetes mellitus can have different inheritance patterns.

When this condition is caused by mutations in the KCNJ11 or INS gene it is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In about 90 percent of these cases, the condition results from new mutations in the gene and occurs in people with no history of the disorder in their family. In the remaining cases, an affected person inherits the mutation from one affected parent.

When permanent neonatal diabetes mellitus is caused by mutations in the ABCC8 gene, it may be inherited in either an autosomal dominant or autosomal recessive pattern. In autosomal recessive inheritance, both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Less commonly the condition is caused by mutations in other genes, and in these cases it is also inherited in an autosomal recessive pattern.

About 1 in 400,000 infants are diagnosed with diabetes mellitus in the first few months of life. However, in about half of these babies the condition is transient and goes away on its own by age 18 months. The remainder are considered to have permanent neonatal diabetes mellitus.