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Qualified, Dedicated Physicians
The rheumatologists at ARA are board-certified in Internal Medicine and Rheumatology by the American Board of Internal Medicine. For over twenty years, their colleagues and patients have relied on their medical expertise, especially in treating rheumatoid arthritis, osteoarthritis, osteoporosis, spondylo-arthropathies, back pain, neck pain, systemic lupus and Lyme disease. Patients benefit from the collective expertise of ARA physicians who meet frequently to review specific cases, new drug treatment protocols and promising research.

As part of their continuing medical education they regularly attend and participate in local and national symposia and conferences. ARA physicians contribute to the community by teaching medical students, interns and residents and fellows from the George Washington University School of Medicine, the University of Maryland and the National Institutes of Health. They also provide lectures to other physicians at regional, national and international symposia, and at area hospitals , as well as conduct community seminars on arthritis and rheumatic diseases. Practice members are on the consulting and medical staff of Holy Cross Hospital, Shady Grove Adventist Hospital, The George Washington University Medical Center, Sibley Hospital, the Washington Hospital Center and Georgetown University Hospital.


Partners in Healthcare
Treating the total person, not just the disease, is the underlying philosophy at ARA. To this end, physicians consider the social and emotional impact of a disease or condition as they develop treatment plans. They encourage patients to express concerns and ask questions. Our physicians know that patients who understand their condition and participate in treatment decisions are more likely and better able to follow treatment plans.

As part of its ongoing effort to share information and educate patients, ARA distributes a newsletter, Rheumors, to all patients. The newsletter contains articles on various aspects of arthritis and rheumatic diseases, answers questions submitted by patients and describes research findings and breakthroughs in the field of rheumatology.


Physician Biographies


Herbert S. B. Baraf, MD, FACP, FACR

Dr. Baraf is a Clinical Professor of Medicine at The George Washington University School of Medicine, a Clinical Associate Professor of Medicine at the University of Maryland School of Medicine and a consultant in Rheumatology for the National Institutes of Health Rheumatology Training Program. He is a Fellow of the American College of Rheumatology and the American College of Physicians. He serves on the Board of Directors of the International Rheumatology Network, an organization of over 750 practicing rheumatologists. He is a member of the medical advisory board for the Scleroderma Foundation of Greater Washington and a member of the Board of Directors for the Arthritis Foundation, Metropolitan Washington, DC Chapter. Dr. Baraf serves as the Managing Partner of Arthritis and Rheumatism Associates. He is also the Director of the research division of our medical practice, The Center for Rheumatology and Bone Research, which he founded in 1982. Dr. Baraf has been recognized as an outstanding specialist in the field of Rheumatology in Washingtonian magazine, Washington Consumers' Checkbook, and Best Doctors in America.

Dr. Baraf received his B.S. degree at the University of Michigan, Ann Arbor, MI in 1969 and his medical degree at S.U.N.Y., College of Medicine, Downstate Medical Center, Brooklyn, NY in 1973. He completed his Internal Medicine training at The George Washington University Hospital, Washington, DC and a Fellowship in Rheumatology at Duke University Medical Center, Durham, NC. He is Board Certified in Internal Medicine and Rheumatology.


Robert L. Rosenberg, MD, FACR, CCD

Dr. Rosenberg serves as the Laboratory Director for Arthritis and Rheumatism Associates, P.C. and the Co-Director of the Osteoporosis Assessment Center. He is a Founding Fellow of the American College of Rheumatology and a member of the American College of Physicians. He is also a member of the Rheumatism Society of the District of Columbia where he has served as president.

Dr. Rosenberg completed a seven year combined program at The George Washington University and The George Washington University School of Medicine where he received his M.D. in 1972. His Internship and first year of his Medicine Residency were at the University of Pittsburgh; he completed his Medical Residency and Rheumatology Fellowship at the University of Tennessee. Dr. Rosenberg has also served as an Epidemic Intelligence Service (EIS) Officer for the United States Public Health Service at the Centers for Disease Control in Atlanta, GA. He is Board Certified in Internal Medicine and Rheumatology and is proud of the recognition bestowed upon him by the medical community by being named an outstanding specialist in the field of Rheumatology by Washingtonian magazine and Best Doctors in America.


Evan L. Siegel, MD, FACR

Dr. Siegel completed a seven-year combined Liberal Arts-Medical Education Program at Boston University where he received his M.D. from the School of Medicine in 1984. His Internship and Residency were served at Montefiore Hospital and Medical Center, Bronx, NY. His Fellowship training was completed in a combined program at the New York University Medical Center and the Hospital for Joint Diseases, New York, NY. He is Board Certified in Internal Medicine and Rheumatology and successfully completed a re-certification program in Rheumatology in November 2000.

Dr. Siegel serves as the Physician Director of Arthritis and Rehabilitation Therapy Services, the rehabilitation division of Arthritis and Rheumatism Associates, P.C. He is a Fellow of the American College of Rheumatology and a member of the American College of Physicians and the Rheumatism Society of the District of Columbia. He has been listed in Washingtonian magazine, Washington Consumers' Checkbook, and Best Doctors in America as an outstanding specialist in Rheumatology.


Emma DiIorio, MD, FACR
Dr. DiIorio serves as Co-Director of the Osteoporosis Assessment Center, a division of Arthritis and Rheumatism Associates, P.C. She is a Fellow of the American College of Rheumatology, a member of the American College of Physicians and a member of the Medical Advisory Board of the Lupus Foundation.

Dr. DiIorio received her B.A. from New York University, New York, NY in 1983 where she was a member of Phi Beta Kappa and a Magnum Cum Laude graduate. She earned her Doctorate of Medicine at New York University School of Medicine where she was a member of Alpha Omega Alpha, a medical honor society. Her Internship and Residency were served at the Mount Sinai Medical Center, New York, NY, and her Fellowship training in Rheumatic Diseases was completed at Baylor College of Medicine, Houston, TX. She is Board Certified in Internal Medicine and Rheumatology and successfully completed a re-certification program in Internal Medicine in the fall of 2000. Dr. DiIorio was recognized as an outstanding specialist in Rheumatology in Washingtonian Magazine and Best Doctors in America.


Alan K. Matsumoto, MD, FACR
Dr. Matsumoto joined Arthritis and Rheumatism Associates, P.C. in March 2002, after nine years on the full time faculty, Division of Rheumatology, at The Johns Hopkins University School of Medicine, Baltimore, MD. He continues as an Assistant Professor of Medicine on the part time faculty at Johns Hopkins. While at Hopkins, as well as treating patients, Dr. Matsumoto directed the rheumatology teaching programs for medical residents at Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center. He co-directed the Johns Hopkins Arthritis Website and served as an ad hoc reviewer for JAMA and Medicine. His research interests included the use of novel therapeutic agents for the treatments of rheumatic diseases. He is a Fellow of the American College of Rheumatology and a member of the American College of Physicians. He was included in Washingtonian magazine's list of "Best Doctors" as an outstanding specialist in the field of Rheumatology.

Dr. Matsumoto was awarded his B.S. degree from Stanford University in 1981 and his medical degree from the University of Illinois at Chicago in 1985, where he was elected to Alpha Omega Alpha, the medical honor society. His Internal Medicine Internship and Residency were served at the University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, where in his final year he was Chief Resident at the Medical Center at Princeton. He completed his Fellowship training in Rheumatic Diseases at Johns Hopkins University School of Medicine in1993 where he was awarded a Howard Hughes Postdoctoral Fellowship for Physicians. Dr. Matsumoto is Board Certified in Internal Medicine and Rheumatology.


David G. Borenstein, MD, FACP, FACR
Dr. Borenstein is a Clinical Professor of Medicine, Division of Rheumatology at The George Washington University Medical Center in Washington, DC. He is Board Certified in Internal Medicine and Rheumatology and is a Fellow of the American College of Physicians and the American College of Rheumatology. He is a member of the 250 physician International Society for the Study of the Lumbar Spine and of the Rheumatology Society of the District of Columbia.

Dr. Borenstein is the author of Low Back Pain: Medical Diagnosis and Comprehensive Management, and Neck Pain: Medical Diagnosis and Comprehensive Management, both textbooks for physicians. His book, Back in Control!! A Conventional and Complementary Prescription For Eliminating Back Pain was released in June 2001 and is written for the lay population as his book Heal Your Back: Your Complete Prescription for Preventing, Treating and Eliminating Back Pain which was released in January 2011. His primary clinical interests are low back pain, neck pain, spinal disorders, and osteoarthritis. Dr. Borenstein has earned the recognition and praise of the medical community by being named as an outstanding specialist in Rheumatology in Washingtonian magazine, Washington Consumers' Checkbook, Who's Who in Medicine and Health and Best Doctors in America. He is currently serving as the President of the American College of Rheumatology and is the 2011 recipient of the Marriott Lifetime Achievement Award which was bestowed upon him for his outstanding accomplishments and lifetime achievements in the field of rheumatology.


Robert J. Lloyd, MD, MACR
Dr. Lloyd is a graduate of Providence College, Providence, RI and Georgetown University School of Medicine, Washington, DC where he was elected to Alpha Omega Alpha medical honor society and was the recipient of the Physiology and Biophysics award. He served his Internship, Residency and one year of Fellowship training at Georgetown University Medical Center. He completed his second year of Fellowship training at the Veteran's Administration Hospital, Washington, DC. He is a Clinical Associate Professor of Medicine at Georgetown University School of Medicine and is Board Certified in Internal Medicine and Rheumatology. Dr. Lloyd was recognized in Washingtonian magazine as an outstanding specialist in the field of Rheumatology, Washington Consumers' Checkbook and Best Doctors in America.

Dr. Lloyd has served on numerous committees of the Medical Society of the District of Columbia including the Chairmanship of the Rheumatology Section. He is a recipient of the Clinical Faculty Award from the Department of Medicine at Georgetown University School of Medicine and has also been honored with their Vicennial Medal. He has been a committed volunteer for the American College of Rheumatology (ACR) and in 2002, they honored him with the Paulding Phelps award for outstanding service on behalf of Clinical Rheumatology and the American College of Rheumatology. In the fall of 2010 he was awarded the College’s distinguished title of Master (MACR). Dr. Lloyd has been engaged in the private practice of Rheumatology in the Washington, DC area for the past 30 years.


David P. Wolfe, MD, FACR
A native Washingtonian, Dr. Wolfe graduated Cum Laude from Amherst College, Amherst, MA where he received his BA in 1990. He received his Medical Degree from Georgetown University School of Medicine, Washington, DC, in 1995. Dr. Wolfe completed a residency in Internal Medicine and Pediatrics at Tufts University's Baystate Medical Center, Springfield, MA. While at Baystate, he was honored with the House Staff/Fellow Citation for Excellence in Teaching Award, given by the Tufts University School of Medicine, Class of 1998.

From August 1999 - June 2002, Dr. Wolfe was employed by the Chinle Comprehensive Health Care Facility (Chinle Hospital), of the Navajo Area Indian Health Service. During that time he served as a staff physician as well as the Medical Director of the Outpatient Department, and as Project Manager for an Outpatient Redesign and Expansion project. In July 2002, he received the Superior Administrative Service Award from the hospital.

In June 2004, just prior to joining Arthritis and Rheumatism Associates, P.C., Dr. Wolfe completed a Fellowship in Rheumatology at the University of Pittsburgh Medical Center, Pittsburgh, PA.

Dr. Wolfe will see patients in our DC and Chevy Chase locations. He has experience in all areas of Rheumatology, but has special interests in Fibromyalgia, Rheumatoid Arthritis and Osteoporosis.


Paul J. DeMarco, MD, FACP, FACR
Paul J. DeMarco, M.D. earned his undergraduate degree from Georgetown University, Washington, DC and his medical degree in 1990 from Georgetown University School of Medicine where he received a Naval Health Professional Scholarship. After a year of Internship in Family Practice at the Naval Hospital Camp Pendleton, NC, he served the country as the Medical Department Head aboard the USS Denver, an amphibious transport dock from 1991-1993. He returned to training in Internal Medicine at Naval Medical Center San Diego, CA until 1996 and then went on to complete his fellowship training in Rheumatology in 1998 at the Scripps Clinic and Research Foundation, La Jolla, CA where he was selected to the position of Chief Fellow.

Upon completion of his fellowship training, Dr. DeMarco returned to the Naval Medical Center, San Diego, where he had appointments in Internal Medicine and Pediatrics, and was on staff at Children’s Hospital in San Diego as a consulting physician. Dr. DeMarco completed his military service in 2001 as the head of Rheumatology at Naval Medical Center San Diego, and then moved to the Marshfield Clinic, Wausau, WI where he treated adults and children with rheumatic diseases, participated in research and taught for the University of Wisconsin-Madison Medical School.

Dr. DeMarco moved to the DC metropolitan area in 2003 to work on the teaching faculty at the Washington Hospital Center and was co-director of the Rheumatology Fellowship Program. He is an Associate Clinical Professor of Medicine at Georgetown University School of medicine. He has published and lectured in most aspects of rheumatology, but has particular interest in connective tissue diseases in adults and children. Dr. DeMarco is a Board Certified Rheumatologist and is a Fellow of the American College of Physicians and a Fellow of the American College of Rheumatology.


Shari B. Diamond, MD, FACR
Shari B. Diamond, MD earned her B.A. degree in 1996 from Stern College, Yeshiva University, New York, New York where she was a Summa Cum Laude graduate, a Belkin Scholar and a Garden State Scholar. She received her medical degree from Albert Einstein College of Medicine, Bronx, New York in 2001. Dr. Diamond completed her Internal Medicine internship and residency in 2004 and her Rheumatology fellowship in 2007 at George Washington University Hospital, Washington, DC.

From 2004 to 2005 Dr. Diamond worked as a Hospitalist Attending at Sibley Memorial Hospital. In 2006 and 2007 she was the recipient of the DC Rheumatism Society Fellows Forum Poster Award and was accepted for poster presentation at the 2006 and 2007 Annual American College of Rheumatology Scientific Meeting, Washington, DC. Dr. Diamond has co-authored numerous publications and abstracts and has been involved in multiple research projects from 1996 to the present.

Dr. Diamond is a fellow of the American College of Rheumatology and a member of the American Medical Association, the American College of Physicians and the Rheumatism Society of the District of Columbia. She has experience in all areas of rheumatology, but has a special interest in myositis. Dr. Diamond sees patients in our D.C. location.



Angus B. Worthing, MD, FACR
Dr. Worthing is a graduate of Princeton University and the University of Minnesota Medical School, where he was elected to the Alpha Omega Alpha national medical honor society and received the Medical Student Achievement Award. He completed internship and residency in Internal Medicine in 2006 and rheumatology fellowship in 2008 at Georgetown University Hospital, Washington, DC. He also received multiple honors including the Medical Humanities Award and nominations for the String of Pearls Award, given by Georgetown university medical students for excellence in teaching. He is a Clinical Assistant Professor of Medicine at Georgetown University Medical Center.

Dr. Worthing was the president of the Rheumatism Society of the District of Columbia in 2010-2011. He currently serves as the D.C. representative and chairman of the American College of Rheumatology's Affiliate Society Council. He is a member of the American Medical Association and the American College of Physicians.

In 2008, Dr. Worthing published a book chapter on the ways in which rheumatic diseases such as rheumatoid arthritis, psoriatic arthritis, and gout affect the elbow joint. Dr. Worthing sees patients at our Chevy Chase and D.C. locations.



Ashley D. Beall, MD, FACR
Ashley Beall, MD graduated Magna Cum Laude with high honors from the University of Georgia in 1998, where she received both her bachelor of arts in English Literature and her bachelor of science in Cellular Biology. Following her graduation, she earned her medical degree in 2003 from the Medical College of Georgia, where she received multiple honors for academic achievement including the Janet M Glasgow Memorial Achievement Citation Award for the top female graduates in her class, the Merck Manual Award for academic achievement, and induction into the Alpha Omega Alpha medical honor society. Dr. Beall completed her internship and residency in Internal Medicine in 2006 at the Medical University of South Carolina, following which she completed her Rheumatology fellowship in 2008 at the Medical University of South Carolina. During her internship and residency she presented multiple case reviews and medical abstracts at local, regional, and national conferences. Her publications have been featured in academic journals including the Journal of Rheumatology. She has completed and presented clinical research on both Systemic Lupus Erythematosus and Systemic Sclerosis. Her areas of interest also include Rheumatoid Arthritis, Myositis, and Gout.

Dr Beall is board certified in Internal Medicine and Rheumatology. She is a Fellow of the American College of Rheumatology, and has recently been asked to serve as a member of the ACR 2020 Task Force, a national committee to identify future trends and issues in Rheumatology. Dr Beall is a member of both the Montgomery County Medical Society and the District of Columbia Rheumatism Society. She is currently serving as physician director of infusion services at Arthritis and Rheumatism Associates. She sees patients in our Shady Grove and Wheaton locations.



Guada R. Respicio, MD, MS, FACR
Guada Respicio, M.D. earned a B.S. degree in Nursing and an M.S. in Health Evaluation Sciences from the University of Virginia, Charlottesville, VA. During her undergraduate years, Dr. Respicio was tapped for membership in Phi Eta Sigma Freshman Honor Society, Golden Key National Honor Society and Sigma Theta Tau International Honor Society. She graduated from St. George’s University School of Medicine, Grenada in 2004. Dr. Respicio completed her Internship and Residency in Internal Medicine at the University of Connecticut, Farmington, CT in 2007. She was awarded the Philip T. Goldenberg, MD Award for Leadership in 2007. She then served as Chief Medical Resident until 2008. In 2010, she completed her Rheumatology Fellowship at the University of California, San Francisco, CA.

Dr. Respicio has worked as a Registered Nurse, volunteered for numerous community service projects, served in leadership roles and participated in teaching activities throughout her years of education and training. She has also co-authored numerous publications and abstracts and has participated in multiple research projects since 2000. Her areas of interest include systemic lupus, rheumatoid arthritis, osteoarthritis, Sjogren's syndrome and systemic sclerosis.

Dr. Respicio is a member of the American College of Rheumatology and The American College of Physicians. She will see patients in our Wheaton and Rockville locations.




Justin Peng, MD, FACR
Justin Peng, MD earned a B.S. degree in Physiological Science from the University of California at Los Angeles, CA in 1998 and his Master of Arts in Medical Sciences at Boston University Graduate Medical Sciences in 2001. In 2005 he received his Medical Degree from Boston University School of Medicine. Dr. Peng completed his Internship and Residency in Internal Medicine at Georgetown University Hospital in Washington, DC in 2008. In 2011, he completed his Rheumatology Fellowship at the University of California at Los Angeles, CA.

Dr. Peng has a diverse research, employment, and extracurricular background. Between earning his Bachelor’s and Master’s degrees, he was an Emergency Medical Technician (EMT) for UCLA Medical Center. While in Boston, he served as a CityLab Educator, working as a teacher in a biotechnology laboratory designed to teach high school students research techniques. Before completing his fellowship, he worked as a physician at INOVA Urgent Care. His extracurricular activities have included leading a team of U.S. medical students to teach English at Shanghai 2nd Medical University and working in medical missions in Nicaragua. During fellowship, he was also involved in drafting the new ACR 2010 guidelines for the management of lupus nephritis.

Dr. Peng has co-authored numerous publications in rheumatology and has been the recipient of multiple awards. He is a member of the American College of Rheumatology. His areas of interest include systemic lupus, rheumatoid arthritis, osteoarthritis, gout, and myositis. Dr. Peng will see patients in our D.C. and Chevy Chase locations.




Rachel Kaiser, MD, MPH, FACR
Dr. Kaiser earned a B.A. in English Language and Literature from the University of Chicago, Chicago, IL in 1997 with general honors. While there, she served as a Student Marshal, the highest undergraduate honor bestowed by the university. In 2001, she received her M.D. with an Area of Concentration in Medical Humanities from the University of Pittsburgh School of Medicine, Pittsburgh, PA. Dr. Kaiser completed her Internship and Residency in Internal Medicine from 2001-2004 and served as Chief Resident from 2004-2005 at St. Luke’s-Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons, New York, NY. In 2007, she received a Master of Public Health degree in epidemiology from the University of California, Berkeley and in 2008 she completed her Rheumatology Fellowship at the University of California, San Francisco (UCSF), CA.

Prior to joining Arthritis and Rheumatism Associates, P.C., Dr. Kaiser was on the faculty for several years as an Assistant Professor in the Division of Rheumatology at UCSF. In that position, she taught and mentored medical students, residents, and Rheumatology fellows in the classroom, on the inpatient Rheumatology consult service, and in the Lupus clinic. She was also a member of the UCSF medical school admissions committee.

Dr. Kaiser has received numerous honors and awards including the American College of Rheumatology (ACR) Distinguished Fellow Award. She has been awarded grants from the Arthritis Foundation, ACR, and UCSF in support of her research examining genetic risk factors for thrombosis - or blood clots - in patients with lupus and has presented her work at international meetings as well as authored many publications.

Dr. Kaiser is Board Certified in both Internal Medicine and Rheumatology and is a member of the American College of Physicians, the Arthritis Foundation, and a fellow of the American College of Rheumatology. Dr. Kaiser has experience in all areas of rheumatology and has a special interest in lupus. She also speaks French. She will see patients in our DC and Chevy Chase locations.