Familial Hyperinsulinism

Familial hyperinsulinism is an inherited disorder that causes too much insulin to be produced. Affected individuals tend to be born large and within the first few days of life develop severe hypoglycemia (low blood sugar). Symptoms may include seizures, poor muscle tone (hypotonia), poor feeding, and apnea. If these infants do not respond completely to diet or other therapy, surgery may be done to remove part of the pancreas. Long-term monitoring and management is needed to prevent hypoglycemia, because if left untreated, irreversible brain damage will occur. One of the causes of familial hyperinsulinism is pathogenic variants in the ABCC8 gene.

Familial hyperinsulinism is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant in the gene for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

There are generally no signs or symptoms associated with being a carrier for familial hyperinsulinism. However, the risk to have a child affected with familial hyperinsulinism is increased. Testing of reproductive partners is recommended for carriers of familial hyperinsulinism.

Familial hyperinsulinism occurs in about 1 in 50,000 European newborns. Some other populations have much higher frequencies of familial hyperinsulinism, including Ashkenazi Jewish populations with approximately 1 in 7800 births and Central Finland and Saudi Arabian populations each with approximately 1 in 2500 births.

Genetics Home Reference: Congenital Hyperinsulinism (http://ghr.nlm.nih.gov/)
Genetic Alliance: Familial Hyperinsulinism (http://www.diseaseinfosearch.org/)

OMIM [HHF1: 256450] (http://www.ncbi.nlm.nih.gov/omim)
Familial Hyperinsulinism (http://www.ncbi.nlm.nih.gov/books/NBK1116/)

• Full gene sequencing