Our Doctors

Dr. Joseph Cece founded Oak Brook Allergists in 1962. At that time, he was the only practicing Allergist in DuPage County. Shortly after Oak Brook Allergists was established, Dr. Cece invited a colleague from Michael Reese Hospital, Dr. Harold Leichenko, to join him. Dr. David Knysak joined Drs. Cece and Leichenko in 1988. Dr. Knysak was a Clinical Instructor at the University of Michigan before entering private practice. Dr. Cece passed away in 1992, and Dr. Leichenko retired in 2003. Dr. Knysak's experience has been instrumental in our continuing success. Dr. Raymond Pongonis Jr. joined Oak Brook Allergists in 2014 and is a leading exkpert in food allergies, with a strong interest in pediatric patients. Oak Brook Allergists has grown to four office locations, board certified/board eligible allergists, a support staff which includes registered nurses, experienced receptionists, and our own billing and insurance department.

DAVID J. KNYSAK, M.D.

Experience
Practicing medicine since 1982
Fellowship
Allergy, Asthma and Immunology University of Michigan Medical Center, Ann Arbor, Michigan
Residency
Internal Medicine Jewish Hospital of St. Louis/Washington University
Internship
Internal Medicine, Jewish Hospital of St. Louis/Washington University
Medical School
Northwestern University Medical School
Board Certifications
American Board of Internal Medicine American Board of Allergy and Immunology
Professional Associations
American Academy of Allergy, Asthma and Immunology American College of Allergy, Asthma and Immunology Past President, Illinois Society of Allergy, Asthma and Immunology




RAYMOND M. PONGONIS JR., M.D..

Experience
Practicing medicine since 2012
Fellowship
Vanderbilt University, Nashville, Tennessee
Residency
McGaw Medical Center of Northwestern University, Evanston, Illinois
Internship
McGaw Medical Center of Northwestern University, Evanston, Illinois
Medical School
The Ohio State University College of Medicine, Columbus, Ohio
Board Certifications
American Board of Allergy and Immunology American Board of Internal Medicine
Professional Associations
American Academy of Allergy, Asthma and Immunology Alpha Omega Alpha Honor Society


Jennifer K. Catalfio, PA-C

Education
Master of Physician Assistant Studies Marquette University Milwaukee, WI Bachelor of Science, Biomedical Sciences Marquette University Milwaukee, WI
Board Certifications
Board-Certified Physician Assistant by National Commission on Certification of Physician Assistants Illinois Licensed Physician Assistant




Tammy Laas, APN, MSN, FNP-BC

Education
Master of Science in Nursing (MSN)
Rush University
Chicago, IL
Bachelor of Science in Nursing (BSN)
Lewis University
Romeoville, IL

Board Certifications
Board Certified Family Nurse Practitioner by American Nurses Credentialing Center Illinois Licensed Advanced Practice Nurse

Professional Associations
American Association of Nurse Practitioners
National Association of Pediatric Nurse Practitioners