February 28, 2019
I am writing to you to announce my retirement from the Allergy Asthma Clinic, Ltd. effective the end of
April 2019. This decision was not taken lightly. It has truly been a wonderful career of 30
years here at Allergy Asthma Clinic (not to mention 19 years total of undergraduate, graduate,
medical school, residency, and fellowship training). Yet after careful consideration and
consultation with my family, I felt it was time to step back and hand the practice over to my
excellent associates, Dr. Bart Leyko and Dr. Chris Couch, with help from our terrific FNP Sherri Crespin. I am
in good health and feel it is now time to spend more time with my family. I have a
wonderful wife Mary and two terrific children, Ryan and Rachel, as well as two wonderful parents
who are alive and well here in Phoenix (92 y.o.!). I am also planning to concentrate more on my
teaching and medical research here at the University of Arizona School of Medicine.
Our Allergy/Immunology Board-Certified physicians Dr. Bart Leyko, Dr. Chris Couch, and our FNP Sherri
Crespin will be very happy to take over your care, and they have my highest
recommendations. They are fully capable of meeting all of your needs as valued patients. Please
visit our website, allergyasthmaclinicltd.com, to learn more about their backgrounds and
expertise. Our nursing staff, front office staff and back office staff are truly world class and I am
confident they will continue taking great care of you. If you are currently receiving allergen
immunotherapy (allergy shots), Xolair, Nucala, Fasenra, Dupixent, or IVIG infusions your
treatments will not be interrupted. You may continue them under the direction of one of our
other physicians. If you have any questions or concerns, please contact our office manager Ivy
Christ at the Clarendon office at 602-277-3337. I encourage all of my great patients to remain as members
of our extended Allergy Asthma Clinic family.
You, my wonderful patients, have been the best patients in the world! I thank you for the
opportunity to have been your physician and feel grateful that I was part of each and every one of
your lives. I will miss you. I will not forget you. I know I will see many of you out and about at
times. But, as it is said, there is nothing in life more constant than change.
All my best for your continued health and happiness!
Mark Schubert, MD, PhD