Like most people, Becky and Steve Vivian of Royersford had never heard of metachromatic leukodystrophy (MLD).
It wasn't until their son Eli was diagnosed with the rare neurological disorder that they discovered they were each genetic carriers of the disease, which afflicts one child out of 40,000.
Earlier this week, they discovered that their youngest child, 4-year-old Ella, is also afflicted with the condition. Their two oldest sons are carriers, as are one in 100 people.
Read more about the Vivians and their fight against MLD on Limerick-Royersford-Spring City Patch.