hyperinsulinism

our 6 month old was born with hyperinsulinism and has since had a sub-total pancreatectomy and is now cured.  she got her gene mutation from my husband.  we have 2 other healthy children (all 3 are girls) and we just found out that we are actually pregnant again!  can you tell me the chances of another baby inheriting this same gene mutation?  

[Lisa Kessler, MS, CGC]

Congratulations on your current pregnancy.  As you know, familial hyperinsulinism is characterized by hypoglycemia, which can be severe and diagnosed at different ages from infancy through adults.    In infants it can cause seizures, hypotonia (low muscle tone), poor feeding, and apnea.   The condition is variable and even people in the same family can have symptoms that are mild and severe.  

There are several different genes associated with familial hyperinsulinism.  Two of the genes involved with familial hyperinsulinism are called ABCC8 or KCNJ11.  Changes in these genes are usually inherited in an autosomal recessive way, but more rarely can be inherited in an autosomal dominant manner.  If inherited in an autosomal dominant way, changes in the ABCC8 or KCNJ11 genes must be inherited from the father with the mother’s copy of these genes being lost in order for there to be symptoms of the condition.  

Two other genes associated with an autosomal dominant form of the condition include GCK and GLUD1.  Also, the HADHSC gene is associated with an autosomal recessive form.  

In general, for conditions that are autosomal recessive, both parents are typically carriers of a gene mutation, and the children each have a 25% chance of inheriting the condition.  For conditions that are autosomal dominant, one parent carries a gene change, and he/she has a 50% chance of passing it on to each child.  

I am not able to provide you with specific information about the chance of another baby to inherit this condition because the different possible modes of inheritance.  You would benefit from seeing a genetic counselor to review the specific gene that was involved in your family to understand what the chances are for another baby to inherit this condition.  You can find a genetic counselor through the National Society of Genetic Counselors.  Best wishes to you and your family.