Our Physicians and Nurses

The Arthritis Center has a dedicated staff of professionals that are experts in Rheumatoid Arthritis and related autoimmune diseases:

Karen Rendt-Zagar, MD

Karen E. Zagar, MD is a native of Pennsylvania, where she attended college (majoring in mathematics and chemistry at Clarion State College) and attended medical school (University of Pennsylvania in Philadelphia). She remained at the Hospital of the University of Pennsylvania for her internship and residency in Internal Medicine. She did her fellowship in Rheumatology at Duke University in Durham, North Carolina.

Dr Zagar joined our staff in 2005.  Prior to that, she spent six years on the staff of the Department of Rheumatic and Immunologic Diseases at the Cleveland Clinic Foundation in Cleveland, Ohio. There she served as the Fellowship Education Program Director to train physicians specializing in Rheumatology. She was also a member of the Center for Vasculitis Care and Research, headed by Dr. Gary Hoffman, and has participated in numerous clinical trials related to osteoarthritis, rheumatoid arthritis, and vasculitis.

Dr. Zagar is board certified in both Internal Medicine and Rheumatology, and she is a fellow in the American College of Rheumatology. Dr Zagar is currently Principal Investigator for all research trials and studies performed at Arthritis Center.

Dr. Zagar and her family enjoy numerous outdoor activities, particularly sailing, biking, and gardening. She also plays flute and classical piano.

Tatiana Nagibina, MD

Dr. Nagibina received her medical degree from Minsk State Medical Institute (former USSR). She completed her internship and residence in Internal medicine at The Chicago Medical School as well as fellowship in Rheumatology at the University of Illinois at Chicago.

Before joining our staff in 2011, Dr. Nagibina spent 10 years serving patients in Pinellas County providing Rheumatological care.

Dr. Nagibina is board certified in Internal medicine and Rheumatology and she is a fellow of the American College of Rheumatology.

Dr. Nagibina enjoys travel, theater, and museums.

Kelli Castle RN, BS

Kelli is originally from Pennsylvania. She attended The Pennsylvania State University, majoring in Nursing, and graduated in 1994. She has worked in Cardiology, Out Patient Surgery and Endoscopy.

She enjoys working as an Infusion Nurse because it allows her to build a long-term relationship with her patients. She looks forward to seeing them and following their improvement with the infusions she gives.

She is an enthusiastic Penn State Football fan, and enjoys running and going to the beach with her family.

Gina Raptoulis, DO

Dr. Raptoulis graduated Summa Cum Laude with her bachelor’s degree in Microbiology and Cell Science at the University of Florida in Gainesville, Florida, and her medical degree from Nova Southeastern University College of Osteopathic Medicine in Fort Lauderdale, Florida. She completed her internal medicine residency and rheumatology fellowship at Largo Medical Center and Nova Southeastern University.

Dr. Raptoulis enjoys treating a full range of rheumatologic diseases including, but not limited to, lupus, mixed connective tissue disease, rheumatoid arthritis and osteoarthritis. When not seeing patients, Dr. Raptoulis enjoys cooking, yoga, traveling and spending time with family and friends.

Amy Bockelkamp, DNP, APRN-c

Amy Bockelkamp has been a nurse for over ten years. She graduated from the University of South Florida (USF) with a dual master’s degree in nursing education and adult–gerontology primary care nursing. Since graduating, she has devoted her clinical practice to rheumatology.
She went on to further increase her knowledge by earning a Doctor of Nursing practice from USF, with a clinical focus in rheumatology. She is board certified in rheumatology (RN-BC) by the American Nurses Credentialing Center. In 2019, she received the Anne Strong Award at the annual Rheumatology Nurses Society conference.
She has developed and is currently seeking to implement a program entitled Rheumatology Virtual City: A Digital Workshop for Advanced Practice Nursing Students. She is an adjunct professor/faculty to multiple universities.
Amy Bockelkamp is married and has three spoiled four-legged children: two cockapoos and a maltipoo. Her hobbies include reading, traveling, going to the beach, sewing, playing the piano, and attempting the cello.