About Us


Lansdowne Internal Medicine was founded by Dr. Han-Jong (John) Koh in August 2000 at the Lansdowne office. His philosophy of providing exceptional and patient-centered care was recognized quickly in the community by many word-of-mouth referrals. Soon after, he was recognized by Washington Magazine as a Top Primary Care Doctor. The practice has since grown to include an additional Internal Medicine physician and an experienced nurse practitioner who continue to espouse the same principles of providing high quality care that is individualized to the specific healthcare needs of the patient.

Our Providers

Dr. Han-Jong (John) Koh graduated from MIT with a degree in chemical engineering and earned his medical degree at Medical School of Wisconsin. He completed his residency in Internal Medicine at Dartmouth-Hitchcock Medical Center where he served as chief resident. He moved to Loudoun County and joined an internal medicine group in Lansdowne for 6 years until he opened Lansdowne Internal Medicine in August 2000. He is now offering MDVIP services which provides personalized healthcare with a focus on preventive care.

Dr. Jenna Choi graduated from Wellesley College and earned her medical degree at the University of Maryland in Baltimore. She completed her residency in Internal Medicine at Northwestern McGaw Medical Center with a focus on women’s health. She completed her fellowship in General Internal Medicine and became a clinical instructor at Northwestern University Feinberg School of Medicine. She joined Lansdowne Internal Medicine in November of 2007.  She is now offering MDVIP services which provides personalized healthcare with a focus on preventive care.

Leigh Villaflor graduated from Virginia Tech with a degree in Biology and entered George Mason University in 1991 for her nursing degree. She worked as a clinical nurse at Washington Hospital Center in the Intermediate Coronary Care Unit for 10 years during which time she took care of patients who were pre and post catheterizations and awaiting heart transplants. She was actively involved as a preceptor for new staff and as the charge nurse. She returned to George Mason University to complete her M.S. in nursing and then joined Dr. Koh in August of 2000 at Lansdowne Internal Medicine. She sees patients, provides individualized diabetic teaching, administers IV Reclast and fits patient with holter monitors.

Our administrative staff:

Tina Leach is our Practice Administrator who has been with the practice from the very beginning and throughout all the transitions. She manages the practice and the staff to create a positive patient experience.

In addition, we have excellent nurses and support staff who are all dedicated to providing the utmost in patient care.