Gilbert F. Gelfand, M.D. is a board-certified rheumatologist and fellow of the American College of Physicians (FACP) and the American College of Rheumatology (FACR). He is a Clinical Professor of Medicine at the Keck School of Medicine of University…

Gilbert F. Gelfand, M.D. is a board-certified rheumatologist and fellow of the American College of Physicians (FACP) and the American College of Rheumatology (FACR). He is a Clinical Professor of Medicine at the Keck School of Medicine of University of Southern California (USC). He is also a Certified Clinical Densitometrist (CCD®) and is highly experienced in diagnosis and management of osteoporosis. He has been caring for patients in Whittier area and throughout the Southeast Los Angeles area for more than 30 years.

Dr. Gelfand studied medicine at the Autonomous University of Barcelona in Spain. He completed his medical training in the U.S. at Maimonides Medical Center and Coney Island Hospital, both in Brooklyn, New York. His Rheumatology training was completed at the Long Island College Hospital with rotations through the Hospital for Special Surgery (Cornell) and Downstate Medical Center.

Dr. Gelfand is presently serving as a Chief of Rheumatology at Rancho Los Amigos Medical Center. This is a USC teaching hospital where he actively participates in the training and education of rheumatology fellows and orthopedic residents for 30+ years.

He speaks both English and Spanish, and enjoys the opportunity to use both languages with his patients. In his free time, he is also an avid hiker/mountaineer, runner, reader and enjoys spending time with his wife and two daughters.


Tien-I Karleen Su, M.D., FACR, is a board-certified rheumatologist and a member of American College of Rheumatology. She studied medicine at the University of California, Los Angeles (UCLA) and completed her rheumatology fellowship at the Keck Schoo…

Tien-I Karleen Su, M.D., FACR, is a board-certified rheumatologist and a member of American College of Rheumatology. She studied medicine at the University of California, Los Angeles (UCLA) and completed her rheumatology fellowship at the Keck School of Medicine of University of Southern California (USC). While at UCLA medical school, she was elected into the Alpha Omega Alpha Medical Honor Society and has remained a member since.

She holds many leadership positions including Founder of Rheumatology Private Practice Alliance (RPPA), Chair of American College of Rheumatology Community Practice Council, and Board member of California Rheumatology Alliance. In all these roles, her mission is to empower current as well as new generations of rheumatologists to thrive in private practice and provide superior care to rheumatology patients.

Dr. Su is also a co-founder of Amicus Arthritis & Osteoporosis Center and a principle investigator of several clinical studies on rheumatological conditions including rheumatoid arthritis, lupus, psoriatic arthritis, osteoporosis, scleroderma, Sjogren’s Syndrome, and osteoarthritis. She has been treating patients in the Whittier area and throughout Southeast Los Angeles for more than ten years. She is passionate about serving the Whittier and nearby communities and sees herself practicing in this area for many more years to come.

Dr. Su enjoys traveling, visiting museums, and photography (some of her photographs from her travels are featured here on our website). She speaks English, Spanish, and Mandarin.


Susan Mansourian, M.D., FACR, graduated with summa cum laude from Debrecen Medical School in Hungary. After immigrating to the United States, she completed her residency in Internal Medicine at Rochester Regional Health-Unity Campus in Rochester, NY. She went on to complete her rheumatology fellowship at the University of Kentucky, where she refined her skills in diagnosing and managing complex rheumatologic conditions.

As a member of the American College of Rheumatology, Dr. Mansourian stays up-to-date on the latest advancements in the field and is committed to providing her patients with the highest level of care.

With her empathetic approach, Dr. Mansourian strives to provide each of her patients with individualized care, tailored to their unique needs. She is dedicated to helping patients achieve their best possible health outcomes, and she infuses her passion for rheumatology into every aspect of her practice. 

Outside of her professional life, Dr. Mansourian enjoys expressing her artistic side through painting with watercolor and acrylic. She also values traveling and spending quality time with friends and family. She is fluent in English and Farsi.


Ericsson Trieu, PA-C is a board-certified physician assistant. He graduated from UCLA with a bachelor's degree in physiologic science. He then worked as an EMT on an ambulance in both Orange and LA counties for 2 ½ years. He started his physician as…

Ericsson Trieu, PA-C is a board-certified physician assistant. He graduated from UCLA with a bachelor's degree in physiologic science. He then worked as an EMT on an ambulance in both Orange and LA counties for 2 ½ years. He started his physician assistant training in Nevada in 2013 and relocated back to southern California in 2017.

He initially practiced in primary care where he learned the importance of providing comprehensive care to patients and became well versed in patient education. He brought these qualities to his position at Amicus Arthritis since 2017 where patients have described him as compassionate and detail-oriented. His hobbies include traveling, photography, trying out new foods, basketball, and spending time with his family and wife. He speaks English, Cantonese, and Spanish. We are delighted that Mr. Trieu has joined Amicus Arthritis to provide quality care to all of our rheumatology patients!