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Meet Our Internal Medicine Specialists

At Addison Internal Medicine, we provide comprehensive primary care to address a wide range of medical concerns. Our primary care experts have a wealth of experience in internal medicine and deliver the highest quality primary care to our patients.

From wellness visits to chronic disease management, our team offers individual guidance, treatments, and medical solutions based on your medical history and lifestyle to improve your overall health and quality of life.

We are proud to serve our Addison community and welcome all patients across the Dallas-Ft. Worth Metroplex. For your convenience, our providers offer both in-office and virtual televisits for appropriate conditions. To schedule an appointment, call our office at (972) 733-3090 or book your appointment online.

Dr. J. Shaun Murphy
Dr. Tri T. Nguyen
Dr. J. Shaun Murphy, Internal Medicine
Dr. Tri T. Nguyen, Internal Medicine

J. Shaun Murphy, MD


Tri T. Nguyen, MD


Dr. J. Shaun Murphy, a native of Richardson, TX, attended Jesuit High School and was the salutatorian of his graduating class. His medical training began at the University of Texas Health Science Center in San Antonio, and it ultimately found him completing his residency at Baylor University Medical Center in Dallas.

Dr. Murphy started his own practice in 1999. In 2004 he became a part of Dallas Medical Specialists where he was Chairman of the Board and Medical Director. In 2011, HCA Physician Services North Texas Division was honored with

Dr. Murphy as the Chief Medical Officer. Later in 2012, Dr. Murphy began working with the Senior Center of Dallas Medical Specialists.

Dr. Tri T. Nguyen hails from the Gulf Coast city of Lake Jackson, TX. He received his medical training at the University of Texas Southwestern in Dallas, and he completed his residency at the University of Texas Health Science Center in Houston.

In 2004, Dr. Nguyen began working with Dallas Medical Specialists, and today he provides outstanding internal medicine services in Addison, TX, for a variety of diverse medical conditions.

Dr. Phuong Tran
Dr. Quynh Ton-That
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Dr. Quynh Ton-That, Internal Medicine

Quynh Ton-That, MD

Dr. Quynh Ton-That was born in Vietnam, but his family decided to emigrate to the US in 1978 when he was 9. They settled in Wichita, KS where he grew up and graduated as valedictorian from Maize High School. He received his college education from Wichita State University and a medical degree from the University of Kansas School of Medicine.

After finishing his internal medicine residency at Baylor University Medical Center, he started his medical practice as a hospitalist at Baylor Garland Medical Center in 1999, transitioning eventually to an outpatient practice at Dallas Medical Specialists in 2004. Hoping to continue providing care to the surrounding communities, Dr. Ton-That relocated his practice to Addison Internal Medicine in 2013.

Phuong Tran, MD

Dr. Phuong Tran earned his bachelor’s degree from the University of Houston, after which, he attended the UT Southwestern Medical Center where he earned his Doctor of Medicine in 2006.

After his time in medical school, he completed his residency and became certified in Internal Medicine by the American Board of Internal Medicine.  In addition, Dr. Tran received his Texas State Medical License.

Dr. Tran joined Addison Internal Medicine as an internal medicine specialist in 2016. He provides the highest quality primary health care in North Texas.

Michelle Lor, NP
Uyen Nguyen, PA-C
Uyen Nguyen, PA-C
Michelle Lor, NP

Uyen Nguyen, PA-C

Uyen Nguyen, PA-C, is a certified physician assistant trained in the field of general medicine and preventive care services. She has the experience and expertise to care for our patients properly.

Uyen received her Master of Physician Assistant studies from Mississippi College. She earned her Bachelor’s Degree in biology from the University of Texas at Austin and holds a master’s degree in biology and medical sciences. 

Michelle Lor, NP-C

Michelle Lor, NP-C, is a certified nurse practitioner with extensive experience in internal medicine. Michelle is now accepting new patients as well as treating established patients. She earned her Bachelor’s Degree from the University of Houston, followed by another bachelor’s degree from Texas Christian University. Additionally, she completed her Master’s Degree in nursing at the University of Texas, Arlington. Michelle is fluent in English and Vietnamese.

Sara Heringer, PA-C
Kathryn Davis
Sarah Heringer, PA-C
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Sarah Heringer, PA-C

Sarah Heringer is a certified physician assistant with a positive approach to healthcare. Sarah was raised in the country in rural eastern Montana. Sarah completed a Bachelor of Science degree at Valley City State University in North Dakota. She earned honors as the Biology Student of the Year in 2006. She continued her education at Rocky Mountain College in Montana and achieved a Master’s Degree in Physician Assistant studies in 2009.

Kathryn Davis, PA-C

Kathryn Davis is a certified physician assistant. Following a loved one's illness, Kathryn was compelled to pursue a career in medicine. With a focus on preventive care, Kathryn builds trusting relationships with patients to improve understanding, participation, and overall health outcomes. A Dallas-Fort Worth native, Kathryn completed a Bachelor of Science degree at Abilene Christian University and obtained a Master's Degree in Physician Assistant Studies at UT Southwestern Medical Center. 

Kristen Lund, PA-C, BSN, RN
Kristen Lund, PA-C
AIM headshots Jai'Cee Tudman final.png
Jai'Cee Tudman

Kristen Lund, PA-C, BSN, RN

Kristen completed a Bachelor of Science in Kinesiology at the University of Arkansas Fayetteville before attending Arkansas State University for her Bachelor of Science in Nursing. Most recently, Kristen completed a Master of Science in Physician Assistant Studies at Harding University. Her background in both the nursing and medical models of care gives Kristen a unique perspective on patient-centered care.

Jai'Cee Tudman, PA-C

Born and raised in Amarillo, Texas, Jai'Cee graduated from Wayland Baptist University with a Bachelor of Science in Molecular Biology before completing a Master of Science in Physician Assistant studies at UT Southwestern. Jai'Cee's curiosity and love for science were evident early on, and her fascination with science laid the foundation for her future career. Her journey into the field of medicine is a testament to her resilience, determination, and unwavering commitment to making a difference in underserved communities.

Same-Day and Next-Day Appointments Available

Call our office and a member of our team will be happy to assist you!

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