Katelyn Williar P.A.

We are happy to introduce Katelyn Williar, P.A., who will periodically see urgent-sick patients at Milestones Pediatrics. She currently works part time at Novant-UVA Hospital Emergency Department (PWH & Haymarket). For the past two years, Katie has also been working a part time for a reconstructive plastics and hand surgeon, seeing patients and assisting in the OR for trauma surgeries. In previous years in the Prince William Hospital Pediatrics Emergency Room, she worked Full Time alongside Dr. Shinaishin, Dr. Mackie-Lee and Briony Peachey, CPNP. She has been Board certified PA-C by NCCPA for the past 11 years

Katie grew up in Southern Maryland, and received her undergraduate degree from James Madison University, majoring in Health Sciences and Biology. She went on to receive her Masters in Physician Assistant Studies from George Washington University. In her spare time, Katie enjoys reading, travel and spending time with my husband and 3 sons. She has been bringing her sons to Milestones since we first opened in early 2014.

Susanne Mackie-Lee, M.D. FAAP

Dr. Susanne Mackie-Lee is a Board-Certified Pediatrician who, just before joining our practice, worked for several years as a Pediatrician in the Emergency Department, Well Baby and Inpatient units of Novant UVA Prince William and Haymarket Hospitals. She also served ten years there as Chairman of Pediatric Department and Director of Pediatric Hospitalists. 

Dr. Mackie-Lee completed her Doctor of Medicine at The George Washington University in 1995, followed by completion of Internship and Residency at Georgetown University Hospital.

Dr. Mackie-Lee was born at GW Hospital while her mother was a medical school professor there. She was raised in the DC Metro area, attended high school in Bethesda, MD and also attended GW University where she earned a B.A. cum laude as well as a Masters in Public health. Dr. Mackie-Lee was inspired to specialize in Pediatrics by her own pediatrician, the late Dr. Beale Ong, located on New Mexico Avenue in DC. Dr. Shinaishin and Briony Peachey CPNP have both worked with her at Prince William Hospital for a number of years.

In her spare time she lends a hand to her husband, who runs Mackie’s Bar & Grill in Old Town Alexandria, where they reside.

Briony J. Peachey, CPNP 

Briony Peachey, CPNP, is a Board Certified Pediatric Nurse Practitioner who
has lived in Prince William County for the last 18 years. She has four
children, two boys and two girls.

She was born in England but moved as a young child to Canada. She completed her undergraduate degree at Queen's University in Ontario, Canada, earning a Bachelor's Degree in Nursing Science. After moving to the United States with her family in 1997, she earned a Master's Degree in Nursing Science as a Pediatric Nurse Practitioner from Catholic University, Washington, DC, in 2004.

Briony has worked in pediatrics for the last 25 years, previously as a neonatal intensive care nurse and a pediatric emergency room nurse before becoming a CPNP. She has worked as a CPNP in the Emergency Department of Novant UVA Health Prince William Medical Center since 2005.  She has also worked part time in a private pediatric practice in Stafford VA.

Briony has a special interest and experience with newborn care and education and has experience with breast feeding mothers.  Apart from raising a busy family, and encouraging their sports and academic endeavors, Briony Peachey enjoys spending time doing Crossfit and competing locally with a Master's level competition team.

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Ahmed Tarik Shinaishin, M.D. FAAP

Dr. Shinaishin is board certified by the American Academy of Pediatrics and has been practicing Pediatrics for the past 19 years.  

He has lived most of his life in Northern Virginia and has resided in western Prince William County for the past 16  years. Born in Seattle, WA, he spent his early childhood in upstate NY. At 10 years old, he moved with his family to Northern Virginia.

Dr. Shinaishin completed his undergraduate degree at The University of Virginia and his MD at Marmara University in 1997. He went on to complete his pediatric residency at MetroHealth Medical Center, Case Western Reserve, where he completed an additional year as Chief Resident of Pediatrics. In 2002, Dr. Shinaishin accepted a position as a full time pediatrician at The Children’s Doctor, a private practice in Hagerstown, MD. In 2007 he relocated to western Prince William County, where he accepted a position with Emergency Medicine Associates as a full time Pediatrician in the Emergency Department of Novant UVA Health Prince William Medical Center. His time there gave him extensive experience in acute care and hospital pediatrics.  While working at Novant, he also worked one day a week at  a private practice in Stafford, VA from 2007-2013.

​In his spare time Dr. Shinaishin is an avid swimmer, plays soccer, enjoys cycling and watching his beloved Washington DC sports teams play.  


Reach Us At


Fax: 1-888-972-4515

Virginia Gateway Professional Building

7500 Iron Bar Lane

Suite 120

Gainesville, VA 20155