Join Us for our Greenhill Alumni in Healthcare Panel

Dr. Richard Markus '04, M.D., was born and raised in Dallas, Texas. He graduated from Greenhill School where he played soccer and tennis. Dr. Markus earned his undergraduate degree from the University of Texas in Austin with a major in psychology and graduated with liberal arts honors. Prior to beginning his medical training, Dr. Markus participated in the USC Keck School of Medicine Somos Hermanos Spanish immersion program for healthcare professionals in Quetzaltenango, Guatemala, where he lived and worked for six months. During that time, he taught nutrition classes to children after-school, which sparked an interest in pediatrics.

After returning to the U.S., he earned his medical degree from Texas A&M Medical School. He met his wife, Dr. Rebecca Prengler, while completing his general pediatrics residency at Washington University in St. Louis. They returned home to Dallas where he completed his Pediatric Cardiology fellowship at UT Southwestern Medical School. Dr. Markus is passionate about preventative cardiology including the evaluation of patients with chest pain, syncope, palpitations, hypertension and hyperlipidemia. He also has a special interest in the use of advanced cardiac imaging techniques in the care of young athletes, pediatric oncology patients, and complex congenital heart disease. He is a member of the American Academy of Pediatrics, the American College of Cardiology, the American Heart Association and the American Society of Echocardiography.

Dr. Wendy Parnell Toles '99 is a proud "Forever Club" graduate of Greenhill School class of '99. After graduating from Greenhill, Dr. Parnell attended Emory University in Atlanta, GA. She received her medical degree from Temple University School of Medicine in Philadelphia, PA. She then returned to Dallas to complete her obstetrics and gynecology residency at Parkland Hospital and UT Southwestern. In her final year of residency, she served as chief resident. Upon completing residency, she joined her father, Dr. Winfred Parnell, and her godfather, Dr. Joseph Carlos, in private practice at Carlos and Parnell, MD PA at Medical City Dallas.

This is her 14th year in private practice. Along with providing obstetrics and gynecologic care, Dr. Parnell has remained involved in the medical community. She has served on the Dallas County Medical Society Board of Trustees, Texas Medical Association Insurance Trust Board, and Section Chief of the Obstetrics and Gynecology section at Medical City Dallas. She is currently the Obstetric and Gynecology Department Chair at Medical City Dallas. Dr. Parnell truly loves caring for women in all stages of life. She is appreciative of the trust her patients have in her and her partners. She has also been recognized several times by D Magazine as one of their Best Doctors. 

Dr. Christina Marmol '08 is a family physician practicing in Chicago, IL. Prior to settling in the Midwest, she completed her medical school training at Vanderbilt University in Tennessee and her family medicine residency at Boston Medical Center. It was during residency that she curated her passions for caring for and advocating for the urban underserved.

She cares for patients in an outpatient clinic at PrimeCare, a Federally Qualified Health Center, and on inpatient and labor and delivery wards at St. Mary's Hospital, a community hospital in Chicago. In addition to her clinical practice, she supervises family medicine residents in clinic, in the hospital, and on the labor and delivery unit. Her interests include women’s health, maternal/child medicine, and resident education.