Familial Hyperinsulinism affects insulin levels, which in turn affects blood glucose levels. Patients with the condition release too much insulin. Too much insulin causes blood glucose levels to drop, leading to hypoglycemia. Hypoglycemia can be mild or severe and may recur often or infrequently. Differences are noted even among family members.

Who is at Risk?

Familial Hyperinsulinism is noted in about 1 out of every 50,000 births. The condition is more prevalent in countries where intermarriage between family members is common. In these countries, the rate of disease averages about 1 in every 2,500 live births.

The condition is caused by a mutation to one of seven genes. The ABCC8 gene is most commonly affected and accounts for about 40-percent of all familial hyperinsulinism cases. The KCNJ11 gene is also associated with the condition, but not as frequently as the ABCC8 gene. About 50-percent of cases have no known cause.

Familial hyperinsulinism is an inherited condition. Typically, one altered gene is passed from the father to the child. The father may not show signs of the disorder. In utero, the healthy copy of the gene mutates causing the condition to become active and symptomatic.


Common symptoms of familial hyperinsulinism include:

  • Low blood sugar
  • Lethargy or fatigue
  • Irritability
  • Seizures
  • Difficulty breathing
  • Coma


Diagnosis of familial hyperinsulinism requires genetic testing. Before being sent for testing, a physician will typically take a complete medical history. Blood and urine testing may be completed in an office or via an outside lab. Due to the genetic nature of the disease, parents may wish to undergo genetic testing in addition to affected children.


Treatment of familial hyperinsulinism is focused on controlling blood glucose levels and preventing brain damage. Brain damage may result if blood glucose levels remain low of extended periods or if blood glucose levels drop frequently. When the condition is initially diagnosed, patients may be given intravenous glucose to bring glucose levels back to a safe level. After normalizing glucose levels, patients may be treated with dietary changes and prescription medications to control insulin release. In rare cases, pancreatic resection may be required. A pancreatic resection involves removing all or part of the pancreas.

Life Expectancy

If familial hyperinsulinism is treated early, the condition can be managed for a lifetime with no decrease in life expectancy. If the condition is not treated it can be fatal.