When Abigail was 19 months old, she took a ferry with her mother Gillian across the English Channel during a move from Germany to England. On board, she played with a Belgian toddler whose mother, a doctor, took notice of Abigail’s tight muscles and lack of language. (Gillian asked that we omit their last names to protect their privacy.)
“What syndrome does she have?” the doctor asked Gillian. Gillian didn’t know.
In the coming years, Abigail would receive diagnoses of autism and intellectual disability; she also has recurrent seizures. But it took 20 years to get an answer to the Belgian doctor’s question.
In 2013, Abigail’s doctor, Meena Balasubramanian, enrolled Abigail in Deciphering Developmental Disorders (DDD), a study in which researchers sequence an individual’s genes to find the cause of undiagnosed genetic conditions. In Abigail, they found a de novo, or spontaneous, mutation in a known epilepsy gene called HNRNPU. ...
