Congenital Hyperinsulinism
Synonyms
CHI, familial hyperinsulinism, hyperinsulinemic hypoglycemia of infancy,Overview
Congenital hyperinsulinism (CHI) is a genetic disorder characterized by the overproduction of insulin by the pancreas, leading to dangerously low blood sugar (hypoglycemia), especially in newborns and young children. The overproduction is caused by a dysregulation in the insulin-secreting beta cells of the pancreas, resulting in persistent hypoglycemia.
Symptoms
Congenital hyperinsulinism causes low plasma sugar (hypoglycemia).The symptoms of hypoglycemia in infants are often difficult to identify, as they can be similar to normal infant activities.
Common symptoms of hypoglycemia include:
- irritability
- sleepiness
- lethargy
- excessive hunger
- rapid heart rate
More severe symptoms, such as seizures and coma, can occur with a prolonged low plasma sugar or an extremely low plasma sugar. Common symptoms of hypoglycemia in older children include feelings of shakiness, weakness, tiredness, confusion, and rapid heart rate.
We consider a normal plasma sugar to be >70 mg/dL. Anything less than 60 mg/dL is low, although severe symptoms due to hypoglycemia are not likely unless the plasma sugar is less than 50 mg/dL. Prolonged or severe low plasma sugar can cause seizures and permanent brain damage.
Causes
Congenital hyperinsulinism is caused by genetic mutations that result in inappropriate and excess insulin secretion from the beta cells of the pancreas. It is not related to anything that the mother did during pregnancy. Genetic testing can help to identify the cause of HI.
Diagnosis
The diagnosis of congenital hyperinsulinism is based on history, laboratory findings, and genetic testing. Prompt diagnosis and establishment of effective treatment are essential to avoid neurologic damage.
History
The history of the child is an important piece of the puzzle. This includes information such as when the low plasma sugars started, the timing of the low plasma sugars, whether the baby was born large for gestational age (LGA), any family history of low plasma sugar or unexplained infant deaths, seizures or SIDS.
Laboratory findings
Blood tests drawn when the plasma sugar is less than 50 mg/dL are essential to the diagnosis of HI. In congenital HI, with a plasma sugar 50, you will see suppressed ketones and free fatty acids, an elevated insulin level (although this may not always be captured), and a glycemic response to glucagon, with the plasma sugar rising more than 30 mg/dL when glucagon is administered.
It is important that these samples at the time of a critically low plasma sugar be obtained in an experienced, controlled environment, as we do not want a child to be kept with a critically low plasma sugar longer than is absolutely necessary to make the diagnosis.
Genetic testing
The DNA from a blood sample from the child with congenital HI and each parent can be analyzed to screen for the mutations that cause the most common types of HI. This can be done at commercial laboratories and should be considered in any child suspected to have congenital HI. Contact us for more information on where to have this testing performed.
Prognosis
Sometimes the management of CHI can be complicated. However, once CHI is stable, a degree of normal life can be achieved. Children and young people can have issues with brain development causing problems with memory and processing information so may need additional support in school and the workplace.
When babies and young children are fed through an NG tube, there is a chance that they will ‘forget’ how to feed so it is important to continue feeding small amounts by mouth in addition to NG feeds. Assessment and support from speech and language specialists can help a child to regain the desire to eat and drink by mouth.
In children who have had some or the majority of their pancreas removed, there is a chance of developing insulin dependent diabetes. This is a condition where the remaining portion of the pancreas does not make enough insulin, so insulin has to be injected several times a day.
Many children with this type of diabetes cope well with treatment and have a near normal childhood. Pancreatic insufficiency, where the pancreas cannot release the enzymes needed to break down fats, can also occur, but oral enzyme replacement therapy with meals is an option. With increased knowledge and research, the outcomes for these children are continually improving.
Treatment
Because congenital HI causes dangerously low blood sugars as a result of excess insulin, the treatment for this condition is to try and maintain blood sugars greater than 70 mg/dL. There are two options for treatment of congenital HI, medical therapy and surgical intervention. About 50 percent of children respond to medical therapy, while the other half require surgery for a partial or near total pancreatectomy.