When a child falls ill, two questions quickly come front and center for parents: What’s the problem, and what can be done to fix it? For families whose children have certain congenital disorders, the answers to those questions can be maddeningly elusive. Laboratory tests to diagnose congenital disorders of methylation, such as Beckwith-Wiedemann, Silver-Russell, Prader-Willi, and Angelman syndromes, often come back without a definitive result.  “We can have up to 25% of our results be equivocal for these conditions, and that’s…