Ann Mass M.D. & Paula Kadison M.D.

Ann Mass M.D.

Ann Mass M.D.

Ann Mass M.D. was born and raised in New York City and attended Harvard Medical School, from which she graduated A.O.A. She completed her training in Internal Medicine at Harbor General U.C.L.A. where she was chief resident in medicine and did fellowship work in infectious diseases.  She has had a long-standing practice in internal medicine in Aspen, Colorado and also works as a hospitalist at Aspen Valley Hospital. She has served on numerous committees at the hospital.  She is trained in bone densitometry and certified to read and interpret bone density testing done at the hospital.  Her special interests include early detection and prevention, with specific focus on cardiovascular health, metabolic bone disease with focus on diagnosis and treatment of osteoporosis and infectious diseases. Foremost, she enjoys the challenge of differential diagnosis in internal medicine – addressing and solving complex medical presentations.  Dr. Mass is on the clinical faculty at the University of Colorado Medical School and is active in mentoring students.  Since 2010, she has worked in partnership with Paula Kadison M.D.

Paula Kadison M.D. 

Paula Kadison M.D. 

Paula Kadison M.D. graduated from the Duke University School of Medicine and also did an Internal Medicine Residency there, with fellowship work in Rheumatology and time as Assistant Chief Resident. She then moved to Boston, MA where she trained in research at the Dana Farber Cancer Institute and completed a Medical Oncology fellowship at the Massachusetts General Hospital (MGH).  At the MGH she helped open the Bone Marrow Transplant Unit.   She was a founder and chief medical officer of a medical software company until moving to Aspen in 2006.  In 2010, she joined Aspen Internal Medicine Consultants.  

Dr. Kadison enjoys helping patients with any medical issue but is especially interested in cardiovascular and cancer disease screening and prevention, the special needs of cancer survivors, exercise and high-altitude physiology, and autoimmune/rheumatologic disease.  In addition to her clinical practice as Aspen Internal Medicine Consultants she is a hospitalist at Aspen Valley Hospital (AVH).  

Mackenzie Tulleners NP-C

Mackenzie Tulleners NP-C

Mackenzie Tulleners, NP-C, is a board certified Adult and Gerontology Primary Care Nurse Practitioner. She was born and raised in raised in Carbondale, CO. She attended Colorado State University where she graduated with her BS in Biology and Human Anatomy. Mackenzie went on to attend Denver School of Nursing where she graduated Summa Cum Laude with her BS in Nursing. She worked as a hospital nurse in the ICU, Medical-Surgical and Palliative Care units. While working as a nurse at the University of North Carolina – Chapel Hill in their Medical ICU/step-down unit, she returned to school to pursue her Nurse Practitioner Licensure. She attended Duke University, received her MSN, and graduated with honors. 

Mackenzie and her husband have recently moved back to the Roaring Fork Valley to enjoy family, friends, and the unmatched natural beauty and opportunity for outdoor adventure. She thrives on staying active: enjoying running, hiking, biking, and spending time with family and friends. 

Mackenzie believes in patient-centered care and partnering with patients in a joint problem-solving effort to address health concerns, and achieve each individual’s health goals. She believes in combining the basics of a healthy diet, exercise, lifestyle modifications, and evidence-based medicine to achieve the best possible health outcomes for each patient. 

Mackenzie is currently accepting new patients and is available for walk-in appointments Monday-Friday 8:30am-4:30pm (closed for lunch 1pm-2pm). 


Drs. Mass and Kadison are Assistant Clinical Professors in the Department of Internal Medicine at the University of Colorado.  Our practice incorporates the teaching of third year medical students who come to Aspen from Denver to work with us in the office and at Aspen Valley Hospital.  Students rotate with us for one month while learning the clinical practice of medicine in a rural setting.  This program has been highly regarded by our patients and has received high reviews at the University.  

Aspen Internal Medicine Consultants is one of a select number of practices on the western slope of Colorado that has been awarded a Colorado Primary Care Plus Initiative grant from the state of Colorado.  This grant provides funds for us to explore new ways of communicating with and expanding care to our patient population.