Dr. Lyon-Feeney has practiced Pediatrics and Clinical Genetics for over 20 years. She was involved in research in common diseases such as asthma and obesity at Boston Children's Hospital and the Broad Institute. She has practiced primary care pediatrics in Maine and Massachusetts. She has attended in Clinical Genetics at Boston Children's Hospital, Beth Israel Deaconess Medical Center, and the Brigham and Women's Hospital. She was director of the Cardiovascular Genetics Program and co-director of the UMASS Down Syndrome Program at UMASS Memorial Medical Center. She has been a course leader and small group leader for medical education at University of Massachusetts Chan Medial School.