Meet Our Providers
GI North is comprised of a team of diverse providers dedicated to compassionate, individualized care for every patient, every time.
Dr. Simon Cofrancesco
Dr. Cofrancesco founded GI North in Cumming, GA in the fall of 2011 starting out with 2 employees including his wife, Roxanna, in hopes of starting a successful private practice of his own. Since that time, he has added 5 additional providers, a state-of-the art endoscopy center, in house anesthesia, and a satellite clinic in Alpharetta. All combined, there are now over 50 employees that work at GI North.
Dr. Cofrancesco graduated with honors from Kansas City University of Medicine and Bioscience, followed by his residency at Tufts University affiliate Bay State Medical Center in Springfield, MA. He went on to complete his Gastroenterology fellowship at the Long Island College Hospital in NYC.
After completing his training, Dr. Cofrancesco went to an underserved area in Mississippi to repay his medical school loans, but stayed on for over 15 years after he met his wife, Roxanna Redden, and they started their family of 5 children. Dr. Cofrancesco also served as Chief of Staff at the local hospital in 2014.
Dr. Cofrancesco performs both basic and advanced endoscopic procedures in addition to the medical management of all forms of GI diseases. He remains board certified by the ABIM, and has almost 30 years of experience in Gastroenterology.
His passions in life are his family, adventure in the form of travel, hiking, and diving, and of course, excellence in the care and service he and everyone at GI North provide to all of their patients.
Dr. Sergio Quijano
Sergio Quijano, MD, was born in Lima, Peru. He moved to the U.S. at an early age and grew up in New York City, where he attended the Bronx High School of Science, one of the most prestigious high schools in the country. He graduated cum laude from the State University of New York (SUNY) at Binghamton with a Bachelor of Science in biology. He then attended medical school at New York University School of Medicine. Upon receiving his medical degree, Dr. Quijano completed his internship in internal medicine at North Shore University Hospital in Manhasset, New York. He completed his residency in internal medicine at New York University School of Medicine. From there, Dr. Quijano pursued his clinical fellowship in gastroenterology at SUNY Downstate Medical Center in Brooklyn, New York. Dr. Quijano is double board certified in internal medicine and gastroenterology.
Dr. Quijano is a member of many professional societies: the American College of Gastroenterology, American Society for Gastrointestinal Endoscopy, American Gastroenterological Association, American Medical Association, and New York Society of Gastrointestinal Endoscopy. He has been the recipient of several prestigious medical awards, including the American Society of Gastrointestinal Endoscopy Crystal Award for both diversity minority research and gender research. Additionally, he has written numerous academic papers and posters, taught at both New York University School of Medicine and SUNY Downstate Medical Center, and lectured at local and national conferences.
Dr. Quijano moved to the Cumming, Georgia area in 2014. When not busy at work, he enjoys spending time with his family and loves cooking Peruvian cuisine. Dr. Quijano speaks Spanish fluently. He is excited to join the GI North team in delivering top-quality care and bilingual capabilities to the local community. Dr. Quijano now serves people with gastrointestinal problems in the Cumming area and other Metro Atlanta areas such as Alpharetta, Johns Creek, Suwanee, Duluth, Milton, Dawsonville, and Dahlonega.
Specialty: Gastrointestinal endoscopy
Degrees: Bachelor of Science in biology, SUNY at Binghamton; New York University School of Medicine
Dr. Tyler An
Tyler I. An, DO, was born in Seoul, South Korea, before moving to the U.S. at the age of 12. He lived in Orlando, Florida, until moving to Atlanta, Georgia, to attend college at Emory University. After graduating with a Bachelor of Science in biology, Dr. An worked at Yerkes Research Center for two years before attending the Philadelphia College of Osteopathic Medicine (Georgia campus) in Suwanee, Georgia. He completed his internal medicine residency at Michigan State University (MSU) in East Lansing, Michigan, where he received multiple awards, including Outstanding Junior Resident of the Year, Outstanding Senior Resident of the Year, and the Bernard H. Smookler Endowment Award. Dr. An then completed his gastroenterology fellowship at MSU-affiliated hospitals in Lansing, serving as a chief fellow during the last year of his fellowship.
Dr. An is board certified in internal medicine and gastroenterology. He is a member of the American College of Gastroenterology, American Gastroenterological Association, American Osteopathic Association, and American College of Osteopathic Internists. Dr. An has written and presented a number of academic papers, posters, and oral presentations at various local and national meetings. He was also a clinical instructor and a clinical assistant professor at MSU.
After the completion of his residency and fellowship training, Dr. An moved back to Georgia with his wife, Lydia, and two children, Tobias and Eliana. He is fluent in both English and Korean. Dr. An enjoys spending time with his family and friends and watching and playing sports such as basketball, football, soccer, and golf.
Degrees: Bachelor of Science in biology, Emory University; Philadelphia College of Osteopathic Medicine
Jessica Calabro, MSN, BSN, AGACNP-BC, RN, RNFA
Board-Certified Nurse Practitioner
Jessica Calabro was born and raised near Birmingham, Alabama, where she earned her nursing degree at the University of Alabama at Birmingham in 2007. Shortly after graduation, Jessica moved to Dawsonville, Georgia, and worked as a registered nurse for over 13 years in various specialties, including medical cardiology, endoscopy, and general surgery. In 2020, Jessica graduated from the University of Alabama at Birmingham with a master’s degree in advanced practice nursing with a registered nurse first assist subspecialty. She is board certified by the American Nurses Credentialing Center as an adult-gerontology acute care nurse practitioner. Jessica is a member of the Sigma Theta Tau International Honor Society of Nursing, American Association of Nurse Practitioners, and Association of periOperative Registered Nurses. In her free time, she enjoys spending time with her family and hiking in the North Georgia mountains.
Specialty: Certified Nurse Practitioner
Degrees: Bachelor of Science in nursing, University of Alabama at Birmingham; master’s degree in advanced practice nursing with a registered nurse first assist subspecialty, University of Alabama at Birmingham
Leah Reed MSN, APRN FNP-C
Board-Certified Nurse Practitioner
Leah Reed earned her Bachelor of Science in nursing at Augusta State University in 2015. Before completing her Master of Science in nursing at Georgia State University in 2019, she practiced as a registered nurse in a pediatric ICU, a post-anesthesia care unit, and an adult ICU. Leah also worked as a family nurse practitioner in a primary care setting prior to joining the GI North family in 2021. She is focused on disease prevention, the management of chronic conditions, and assisting patients in their health and wellness through every stage of life. Leah is a nationally board-certified nurse practitioner and a member of the United Advanced Practice Registered Nurses of Georgia’s Atlanta chapter. She is trained to assist doctors in assessment, diagnostics, and treatment for numerous gastroenterological conditions and is excited to be a part of the GI North team.
Leah is originally from a suburb of Atlanta, Georgia, and currently lives in the Alpharetta area. When not at work, she enjoys staying active by cycling, running, and hiking—anything that allows her to enjoy Georgia’s local nature. She also enjoys traveling to national parks and international travel. Leah spends most weekends doing these activities with her friends and family, who make everything more entertaining.
Degrees: Bachelor of Science in nursing, Augusta State University; Master of Science in nursing, Georgia State University
Chief Nurse Anesthetist
Jonnice Grentz earned her Bachelor of Science in nursing from Southern Adventist University in 2000. In 2007, she completed her master’s degree in anesthesiology at Wolford College of Anesthesia. Jonnice is a board-certified registered nurse anesthetist (CRNA). Her career includes the full scope of anesthesia practice in a hospital-based setting and as an independent anesthesia provider in the private practice setting. Jonnice is an active member of the American Association of Nurse Anesthetists and has enjoyed being a CRNA preceptor and mentoring many classes of anesthesia residents over the years. Currently, she is chief CRNA for Gastro Anesthesia Services, providing anesthesia care at the GI North Endoscopy Center. In her free time, Jonnice enjoys date nights with her husband, Daniel, and hiking with him and their two children, Carter and Lauren. Her hobbies include playing tennis, painting, gardening, baking, and decorating cakes.
Specialty: Chief CRNA, GI North Endoscopy Center
Degrees: Bachelor of Science in nursing, Southern Adventist University; master’s degree in anesthesiology, Wolford College of Anesthesia