Our staff has over 50 years of combined medical experience specializing in treating acute disease, chronic disease, and preventive health and wellness.


Michael Maloy MD : Internal Medicine - Board Certified

Michael Maloy MD

Internal Medicine - Board Certified

Born and raised in Yoakum, TX, Michael Maloy, Jr, MD studied biology at the University of Texas at San Antonio before receiving his medical degree from the University of Texas School of Medicine at San Antonio. He completed his residency in internal medicine at the University of Texas Health Science Center-RAHC in Harlingen, TX. While in South Texas, Dr. Maloy served as an Assistant Professor of Medicine, teaching medical students and developing inpatient curriculum. He established Sigma Physician Associates in 2016 with a mission to bridge the gap between inpatient and outpatient settings by providing higher quality of care individualized to each patient. In addition to medicine, Dr. Maloy has other passions; in his free time he enjoys spending time with family, hiking, and lifting weights.

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Katrina Villa FNP-C : Nurse Practitioner

Katrina Villa FNP-C

Nurse Practitioner

Katrina Villa was born and raised in Port Lavaca, Texas. She began her career in healthcare as a Licensed Vocational nurse while obtaining her nursing degree from University of Texas at Arlington in 2012. She then worked as a Registered nurse in San Antonio in the post-acute setting caring for patients in med-surg, orthopedic and neuro-rehabilitation. She earned her Master of Science at Chamberlain College of nursing. She holds a national board certification by the American Academy of Nurse Practitioners as a Family Nurse Practitioner. She enjoys caring for patients in both inpatient and outpatient settings.  In her spare time, she likes to read books, work out and spend time with her family.

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Kathryn Makarevich FNP-BC : Nurse Practitioner

Kathryn Makarevich FNP-BC

Nurse Practitioner

Kathryn Makarevich is a Board Certified Family Nurse Practitioner. Kathryn is from California where she completed her Bachelor’s degree in Nursing. She continued her education and graduated magna cum laude from Walden University earning a Master’s degree with a specialization in FNP in 2015. Kathryn’s clinical interests include acute care, geriatrics, and preventative care. In her spare time Kathryn enjoys spending time with her family and friends, watching movies, and exploring San Antonio.

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