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Medical Providers

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Mark Dwinell, MD

Internal Medicine

I was born and raised outside San Diego, CA where I also obtained my Bachelor Of Science degree from Point Loma College in 1983. After briefly working in the pharmaceutical industry, I attended Jefferson Medical college in Philadelphia, PA, graduating in 1991. After an Internal Medicine residency at Virginia Commonwealth University in Richmond, VA. I joined the United States Air Force as a Flightsurgeon, separating as a Major. Moving to Austin in 1999, I was one of the founding members and executive staff for Hospital Internists of Austin where I practiced for 15 years. My wife Emely and I married in 2013 in Marathon, TX and afterwards moved to take a Chief of Outpatient Internal Medicine at San Juan Regional Medical Center, as well as Medical Director for the San Juan County Detention center in Farmington, NM. During the beginning of the Covid pandemic I took a position as an Internist in Saipan, CNMI for 1 year, prior to moving to Alpine TX where I hope to stay and practice for as long as the state will have me. Along the way I raised two children, played guitar in several bands, and travelled about everywhere I could think to travel. I'm making up the rest of the story as I go.


Edith Simmons, MD
Internal Medicine/Nephrology

Dr. Edie Simmons is board certified in Internal Medicine and Nephrology, and practiced in Austin for 15 years before relocating to West TX to be closer to family.  She has expertise in the management of hypertension and kidney diseases, including caring for patients on dialysis and those with kidney transplants.  She was selected as a Top Doctor 2020 in Austin Monthly Magazine, and serves on the End-Stage Renal Disease Network of Texas.


She joined PCHS in Sept 2020, and practices Internal Medicine and Nephrology in Marfa, Presidio, and Alpine.  She has a special interest in kidney diseases and home dialysis.  She graduated magna cum laude from University of Mississippi Medical Center in 1997, where she also completed her Internal Medicine residency in 2001.  She completed her Nephrology fellowship training at Vanderbilt University in Nashville, TN in 2004.  She enjoys spending time with family, hiking, camping, gardening, and cooking.


Emily Sliz, MD

Family Medicine

Emily Sliz grew up in the hill country outside of Austin, TX. She completed her undergraduate studies in St. Paul, Minnesota. After college she returned to Austin to work as a nursing assistant for three years before applying to medical school. She went to medical school in Dallas, TX followed by family medicine residency in Fort Worth, TX. During residency she completed additional training in surgery, obstetrics and HIV. She also had the opportunity to travel and study medicine in Senegal, Ghana, Haiti, France, Cambodia, India and Uganda. She is happy to be in West Texas and looks forward to getting to know the region. 

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Adrian Billings, MD, PHD, FAAFP

Chief Medical Officer

Dr. Billings serves as Associate Professor of Family and Community Medicine at Texas Tech University School of Medicine.  Medical students and family medicine residents routinely rotate with Dr. Billings, and he has been recognized with teaching awards from both Texas Tech University Health Sciences Center-Permian Basin and the University of Texas Medical Branch.  In 2015, the Texas Academy of Family Physicians honored Dr. Billings with the 2015 Exemplary Teaching Award for his work with precepting medical students.  In 2015, Dr. Billings also became director of the Texas Statewide Family Medicine Preceptorship Program. 
Dr. Billings currently serves as chief of staff of Big Bend Regional Medical Center, a critical access hospital, in Alpine, Texas.  Additionally, Dr. Billings serves as Co-President of the Presidio-Ojinaga Binational Health Council and as Medical Director for the City of Presidio Emergency Medical Services.

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William Mason, FNP-C

Nurse Practitioner

William Mason, is a Certified Family Nurse Practitioner that was born and raised in Eagle Pass, Texas.  He graduated with his Bachelor of Science in Biology with a concentration in immunology and microbiology from the University of Texas at San Antonio.  He then obtained his Masters of Nursing Degree from Marquette University and completed his Family Nurse Practitioner certification at Angelo State University.  He is recently moved to Alpine and is eager to be serving the local communities of Alpine, Marfa, and Presidio.  He looks forward to taking care 0f patients of all ages and being part of the community.

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Jose Soto-Hernandez MSN, APRN, FNP-C

Nurse Practitioner

I was born and raised in Ojinaga, Chihuahua, Mexico, and at 18, I moved to Presidio, TX.
In 2002 I graduated from Presidio High School, and in 2007 I graduated from Sul Ross State
University with a License Vocational Nurse degree.  I practiced as an LVN in various settings,
including nursing homes, home health, and the local clinic. In 2017 I attended Midland College
and obtained an associate degree in nursing. From 2018 to 2022, I worked at Big Bend Regional
Medical Center Emergency Department. While working the night shift in the emergency
department, I pursued a Bachelor of Science in Nursing (BSN) from the University of Texas at
El Paso and completed it in 2019. In December 2022, I finished a Master of Science in Nursing
focusing on family practice across the lifespan with a GPA of 4.0. During my clinical rotation,
Dr. J. Ray, Dr. K. Ray, Dr. Simmons, and Dr. Billings were my preceptors in Presidio, Marfa, and
Alpine, TX. This experience prepared me to provide care to my community. In April 2023, I
joined Preventative Health Care Services to practice as FNP. I am delighted to return to Presidio,
TX, and provide excellent medical care to the public in their native language Spanish.

Patrick Daly, MD

Internal Medicine

Presidio was my family’s hometown.  We eventually moved to Midland.  There I attended Odessa Junior College, later transferring to and graduating from the University of Texas at Austin with a degree in biology.  After graduation, I found employment in Dallas with the Food and Drug Administration.  There we monitored and tested food products for safety.  After five years there, I was accepted at Texas Tech Health Sciences Center medical school.  I graduated as an MD in 1983.  From there I began private practice in Dallas as a Board Certified Internal Medicine physician that was to last 34 years until my retirement in December 2020. I am pleased to be part of the PCHS team as a part time physician participating in the care of patients back in my home town and Marfa.

Behavioral Health Providers

Eleazar Cano, LPC

                      Bio coming soon


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