Welcome new faculty members to the Department of Medicine and UMMC!

Samuel Davidson, MD


Hometown: Jackson, Mississippi

Residency: UMMC Medicine-Pediatrics

Division: Hospital Medicine

Tell us about yourself. I was born and raised in Jackson, attended Ole Miss for undergrad, and attended UMMC for medical school and residency. I am a big fan of Ole Miss sports and the NBA, I love reading science fiction and fantasy. 

What are you most looking forward to working at UMMC? Continuing to work in the collegial atmosphere UMMC offers, working with medical students and residents, and getting to serve the people of Mississippi.

Issac M. E. Dodd, MD


Hometown: London, England, UK

Residency: Internal Medicine, White River Health System

Division: Hospital Medicine

Tell us about yourself. It’s a joy and privilege to be here at UMMC! I earned my undergraduate degree and a master’s degree at the University of South Florida in Tampa Bay and then moved to the Washington, DC metro area for medical school at Howard University College of Medicine. In Baltimore, I earned an MPH from Johns Hopkins University and then moved to rural Arkansas to complete residency in Internal Medicine at White River Health System. I have a background in software engineering, which included clinical software and medical device development. My Christian faith is important to me. In my off time, I enjoy playing the guitar, eating good food, and watching movies with my wife Kristen.

What are you most looking forward to working at UMMC? The relationships! I look forward to getting to know my colleagues in the Department of Medicine.

Matthew Elliott, MD


Hometown: McComb, Mississippi

Residency: UMMC Internal Medicine

Fellowship: UMMC Allergy and Immunology

Division: Allergy and Immunology

Tell us about yourself. I grew up in McComb, Mississippi, which is quite a small town in the southern part of the state but in a great location. I attended Millsaps College here in Jackson where I received a bachelor’s degree in mathematics. I then attended medical school and completed my internal medicine residency here at UMMC. I wanted to pursue a fellowship and ultimately became most interested in allergy & immunology which I also went on to do at UMMC. In my free time I enjoy travelling and spending time with friends and family.

What are you most looking forward to working at UMMC? Looking forward to taking care of the many great patients we have here at UMMC.

John Caleb Grenn, MD


Hometown: Hattiesburg, Mississippi

Residency: UMMC Medicine-Pediatrics, Chief Resident in Pediatrics

Division: General Medicine and Hospital Medicine

Tell us about yourself. I grew up in Hattiesburg, Mississippi, graduated from The University of Southern Mississippi where I majored in chemistry and ran on the track and field team, then came to UMMC for medical school. After completing my Med-Peds residency, I spent a year as a Chief Resident in Pediatrics. I’m happily married to Emily Grenn, the coolest surgery resident at UMMC, and am a proud dad to Maeve, my daughter born this past March. We’ve got a fun, sweet, fluffy dog named Ellie, and I’m a huge book nerd. Catch me at Lemuria Books or on my porch in Fondren digging into something good I brought home.  

What are you most looking forward to working at UMMC? I can’t wait to start in my new roles at UMMC in Internal Medicine and Med Peds—working inpatient and outpatient and being able to see both adults and some kids is the real deal dream job. What makes it better is that I will be able to teach students too—I’m thrilled to be starting as a co-course director for IMP-2 with Dr Lyssa Weatherly this year. I’m also looking forward to being the faculty sponsor for the medical student book club, Literati Medicus. 

Charles Grogan, MD


Hometown: Brandon, Mississippi

Residency: UMMC Internal Medicine

Fellowship: UMMC Allergy and Immunology

Division: Allergy and Immunology

Tell us about yourself. After graduating from Mississippi College for my undergraduate degree, I attended UMMC for medical school, residency, and fellowship. My lovely wife teaches at Northwest Rankin Middle School and both of our families live in Mississippi. I enjoy tinkering with computers and playing board games with friends.

What are you most looking forward to working at UMMC? My colleagues in both the adult and pediatric allergy departments have been phenomenal mentors and friends, and I look forward to continue working with them.  

Mobin Kheirkhahan, MD


Hometown: Sary, Iran

Residency: UMMC Internal Medicine

Division: Hospital Medicine

Tell us about yourself. I grew up in Sary (a town south of the Caspian see), and at the age of 18 I, along with my twin brother, moved to Tehran (the Capital) and went to medical school at Shahid Beheshti University of Medical Sciences (SBMU). I met my wife at the very end of my medical school years which made the cold weather of Tehran way more enjoyable. Ever since, the two of us have been to so many places together! I was fortunate enough to complete Internal Medicine Residency at UMMC. Favorite pastimes include reading, especially history books, playing chess and (now very rarely) playing soccer. I am a soccer fan and I still follow European leagues and watch their games when time permits.

What are you most looking forward to working at UMMC? I look forward to working with faculty and colleagues that I trained with during my residency. UMMC feels like family to me now and I never even thought about moving somewhere else.

Alejandro Lemor, MD, MS


Hometown: Lima, Peru

Residency: Icahn School of Medicine at Mount Sinai St Luke’s, New York

Fellowship: Cardiology and Interventional Cardiology, Henry Ford Hospital, Detroit, MI

Division: Cardiovascular Diseases

Tell us about yourself. :   I grew up in Peru, where I did my medical school and masters degree. I completed my Internal Medicine residency at Mt Sinai St Luke’s Hospital in New York, then I did my fellowship in Cardiovascular Disease at Henry Ford Hospital, where I was Chief Fellow from 2020-2021, and then completed additional year of Interventional Cardiology Fellowship.   I like traveling, cooking/eating, and playing and watching sports.

What are you most looking forward to working at UMMC? I look forward to offering state-of-the-art high-risk coronary procedures to cardiovascular patients in Mississippi in order to improve their quality of life and survival.  I also look forward to caring for patients in underserved areas and provide them with excellent clinical care.

Teresa Moll, MD


Hometown: Brandon, MS

Residency: UMMC Medicine-Pediatrics

Fellowship: UMMC Endocrinology

Division: Endocrinology

Tell us about yourself. I grew up in Brandon and have been around UMMC for quite some time. I credit my love for the medical field to both my parents – my mom a nurse at the VA, and my dad a pediatric endocrinologist at UMMC. I graduated from Mississippi College with a BS in nursing and worked at UMMC on the inpatient Hem/Onc floor. It was my time there that I fell in love with not just patient care but with that desire to know more behind what my patients were going through. This desire to know more pushed me to pursue a career as a physician. I graduated from UMMC Medical School where I also completed my Med-Peds residency and Adult Endocrinology fellowship. I chose Endocrinology because of the many pathways involved and how much this system can affect an individual. I also credit my dad, whose footsteps I literally followed during weekend rounds as a kid, for the decision. I watched him care not only for his patients but their family – many of whom I have had the pleasure of caring for as a current provider.

What are you most looking forward to working at UMMC? I look forward to the continued collaboration with my attendings and to the opportunity to teach students of all levels just as my dad taught me.

Ashley Villarreal, MD


Hometown: Hattiesburg, MS

Residency: UMMC Medicine-Pediatrics and Chief Resident, Internal Medicine

Division: General Medicine and Hospital Medicine

Tell us about yourself. Although born in Illinois, I am otherwise a lifelong Mississippian. Raised in Hattiesburg where I also attended undergrad at Southern Miss, I then moved to Jackson first as a researcher then to attend medical school. I chose to stay here for residency and serve an additional year as an Internal Medicine Chief Resident. In my free time, you’ll find me going for a run through Fondren, reading at a coffee shop, dining out, traveling with friends, playing soccer, dancing at a concert or spending time with my favorite people in the world, my niece and nephew. 

What are you most looking forward to working at UMMC? UMMC has already been home for me through multiple phases of my medical journey, and I can’t wait to continue my career here. I will be working on the wards and in the clinic and serving as the associate program director for the Med-Peds residency.

Timothy Yen, MD


Hometown: Rockville, Maryland

Residency: Methodist Dallas Medical Center, Dallas, Texas

Fellowship: Massachusetts General Hospital and Brigham and Women’s Hospital Combined Nephrology Program, Harvard Medical School, Boston, MA

Division: Nephrology  

Tell us about yourself. I majored in History at Emory University before matriculating to Duke-NUS Graduate Medical School. I completed residency and my chief year at Methodist Dallas Medical Center before following my love of kidneys to Boston where I did my nephrology fellowship. I also earned a master’s degree in Medical Science in Clinical Investigation from Harvard Medical School. These days, I enjoy traveling, spending time with family, and indulging in sodium-rich foods.

What are you most looking forward to working at UMMC? I look forward to working with the great colleagues I’ve met here and pursuing my academic and research interests.

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