Advances in genetic testing offer new insights to parents who have a child with a rare but serious form of epilepsy, epileptic encephalopathy (EE), found in one of about every 2,000 births and characterized by developmental disabilities as well as horrible seizures.
“New ways of sequencing the human genome mean geneticists and genetic counselors have much more to say to parents who wonder if future children might carry the disease,” says Dr. Heather Mefford, associate professor of pediatrics (genetic medicine) at University of Washington School of Medicine and Deputy Scientific Director of the Brotman Baty Institute for Precision Medicine, co-senior author of findingspublished this week in the New England Journal of Medicine.
A big question from any parent of a child with EE is, “What are the odds that our other children might have this condition?” For decades, parents whose child had epilepsy were told there’s a 1 to 5 percent chance that other children might inherit the mutation. This was based on clinical evidence – the numbers of reoccurrences physicians saw in the clinic.
But armed with more precise testing, the geneticists found parental mosaicism that wasn’t easily detected before in about 10 percent of families, putting these families at higher risk of passing the mutation to another child. What this means in practical terms is that this small group probably accounts for most of the reoccurrences. For some parents, there’s good news: if this parental mosaicism was not detected, your odds of having another such child with epilepsy could be much less than 1 percent.