About
Comprehensive Rheumatology Center
At Comprehensive Rheumatology Center, we believe every patient deserves care that treats the whole person — not just the diagnosis. Located at 23067 Ventura Blvd, Suite 200 in Woodland Hills, CA, we proudly serve patients throughout the West San Fernando Valley and Conejo Valley.
Our care team brings together four dedicated providers who share a common goal: helping patients with complex autoimmune and inflammatory conditions live fuller, more comfortable lives. Nazanin Firooz, MD, FACR, is a board-certified rheumatologist and founder of our practice, known for her expertise in integrative and holistic rheumatology. She is joined by Phillip Aleksiejuk, MD, a board-certified rheumatologist with a thorough, patient-centered approach; Rana Taherian, MD, a board-certified rheumatologist who brings a wealth of experience and dedication to personalized care; and Sabrina Roofian, PA-C, whose warmth and attentiveness make every patient feel heard and supported.
We specialize in rheumatoid arthritis, lupus, psoriatic arthritis, ankylosing spondylitis, gout, fibromyalgia, and more. Our on-site infusion suite offers biologic IV therapies, and our integrative approach blends conventional rheumatology with holistic treatments tailored to each patient.
We accept most major insurance plans and welcome both referred and self-referred patients. Call us at (818) 598-0000 — we’d love to help.
Meet our Team
Nazanin Firooz, MD, FACR
Dr. Firooz is board-certified in Rheumatology and Internal Medicine. She is an active member of the American College of Rheumatology, and is affiliated with the Department of Rheumatology at Cedars Sinai Medical Center. She received her medical degree from the University of California at Irvine, and completed her residency at University of California, Los Angeles (UCLA) and Los Angeles Veteran’s Hospital. She trained at Cedars Sinai Medical Center for her fellowship in rheumatology.
Dr. Firooz has been published in peer-viewed medical journals and has presented her research in several national rheumatology meetings. She is the recipient of a research award for her presentation at the American college of rheumatology in Washington, D.C.
Realizing the rapidly evolving nature of the field of rheumatology, with new discoveries and treatments that can improve the lives of many patients, Dr. Firooz keeps her commitment to her patients up-to-date by attending the Carl Pearson rheumatology update meeting at UCLA and the American College of Rheumatology scientific meeting every year. She reviews the latest discoveries in the field with several other rheumatologist at the monthly journal club meetings at Cedars Sinai. She prides herself at offering her patients the latest in diagnostic approach and available treatments.
In her free time, Dr. Firooz enjoys traveling, oil painting and salsa dancing. She is fluent in English, Farsi, and Medical Spanish.
Phillip Aleksiejuk, MD
Dr. Aleksiejuk is a board certified physician in both Rheumatology and Internal Medicine. He completed Rheumatology fellowship training at the University of Southern California (USC).
Originally from Toronto, Canada, he realized at a young age that he wanted to pursue a career in medicine after spending countless hours filing medical records at his father’s medical practice. He trained at SUNY Upstate Medical University where he found his passion for diagnosing and treating autoimmune disease.
Dr Aleksiejuk understands the value of comprehensive medical care especially in Rheumatology, given the chronicity and multi-systemic nature of the conditions. He finds immense joy in establishing long-term relationships with his patients and works relentlessly to improve their quality of life. With all of the exciting developments in the field, he strives to formulate individual treatment plans while maintaining a holistic approach.
Outside of medicine, Dr. Aleksiejuk loves to spend time with his family, travel and follow everything related to sports.
Sabrina Roofian - PA-C
Meet Sabrina, a dedicated Physician Assistant (PA-C) with a strong academic foundation and a passion for patient-centered care. She earned her undergraduate degree from UC Santa Barbara before going on to complete her Master’s training at Loma Linda University. Sabrina brings a dynamic and well-rounded clinical background, with experience in both urgent care and rheumatology. This unique combination allows her to approach complex autoimmune and musculoskeletal conditions with both precision and a broad perspective, ensuring patients receive thoughtful, comprehensive care.
Known for her approachable demeanor and attention to detail, Sabrina is committed to helping patients better understand their conditions and feel confident in their treatment plans. Whether managing chronic rheumatologic diseases or addressing acute concerns, she strives to create a supportive and collaborative healthcare experience for every patient she serves.
Kamari Calloway
Kamari is our Office Administrator. She offers support and troubleshooting to our staff, office, and patients. She coordinates seamless operations of the office, while maintaining policies and procedures. With an interest in healthcare administration and informatics, she strives to utilize her growing experience and skills to further her career in the medical field. In her free time, she enjoys going to restaurants, spending time with family and friends, and traveling.
Tannia Villalobos
Tannia began her journey with our practice in 2014 as a student and has since grown into an essential, dedicated member of the organization. Over the past decade, she has advanced into the role of Biologics and Infusion Coordinator, overseeing the infusion and injectable department — managing specialty medication care, insurance authorizations, coordination with specialty pharmacies, and ensuring timely delivery and administration of therapies.
She remains deeply committed to supporting patients through every step of the process, whether navigating prior authorizations, securing copay assistance, or connecting patients with free drug programs. A certified phlebotomist and IV technician, she brings both clinical skill and precision to the in-house infusion center, while also playing an active role in supporting and growing the practice’s in-house pharmacy to streamline access to specialty medications.
Outside of work, Tannia enjoys cooking, arts and crafts, and spending time with her family. A proud mother of two, she values the balance between her professional growth and her family life. After more than 10 years with the practice, she continues to view the team as a second family and takes great pride in contributing to its growth, evolution, and success.
Suman Rizvi
As the Operations Administrative Coordinator, Suman helps oversee administrative processes, supports office operations, and works to improve systems that enhance both the patient and staff experience. She earned her Bachelor of Arts degree in Communication with a minor in Public Relations from Chapman University, bringing strong organizational and interpersonal skills to everything she does.
She enjoys finding ways to streamline workflows, improve efficiency, and support the team behind the scenes to help the practice run smoothly. Outside of work, she enjoys staying active through fitness, Brazilian Jiu-Jitsu, and dancing, as well as spending time with family and friends.
Jamie Leongzon
As a medical assistant, Jamie is responsible for taking patient vitals, asking medical history questions to make sure our patient charts are up to date, and giving injections. If she is not helping out in the back, you can find her in the front answering phones and helping in the check-in and check out process. She has always had a passion for the medical field and hopes to one day use the tools she’s learned here to further her skills in her future career. Outside of work she enjoys singing, traveling, or dancing.
Tatiana Ibanez-Chavez
As the receptionist at our rheumatology center, Tatiana enjoys being one of the first people patients meet when they visit or call our office. She’s passionate about creating a welcoming, supportive environment and helping patients feel comfortable throughout their care journey. Whether she’s scheduling appointments or answering questions, she strive to make each interaction positive and helpful.
Outside of work, she enjoy spending time with her family and friends, exploring new restaurants, staying active, and relaxing with a good book or movie.
Millie Perez
Millie is a Medical Assistant who is passionate about helping others and making patients feel supported and cared for. Working closely with patients has reinforced her desire to pursue a career as a registered nurse, where she hopes to continue providing compassionate care and making a positive difference in the lives of others. In her free time, she enjoys watching movies, attending music festivals, and spending quality time with her friends and family.
America Jimenez
America is a medical assistant who is passionate about listening to each patients’ individual needs and circumstances. She assists with rooming patients, taking vital signs, administering injections, and supporting the front office by answering phone calls and scheduling. She earned her Bachelor’s degree in Biopsychology from University of California, Santa Barbara and is currently in the process of applying to medical school. America is passionate about helping patients overcome barriers that stand between them and care. Outside of work , America enjoys soccer, going to the beach, listening to music, and fashion.
Alejandra Contreras
Alejandra is a dedicated Medical Assistant who enjoys helping patients feel comfortable and cared for throughout their visit. She assists with rooming patients, taking vital signs, administering injections, and supporting the front office by answering phone calls and helping patients schedule appointments.
She earned her Bachelor’s degree in Biology from California State University, Northridge, and is currently pursuing a Master’s degree to become a Physician Associate. Alejandra is passionate about healthcare and values the opportunity to build meaningful connections with her patients while making a positive impact on their lives.
Outside of work and school, Alejandra enjoys spending time at the beach, exploring local hiking trails, and making memories with friends and family.
Sharzad Firooz
Sharzad has a certificate in Mindfulness Based Stress Reduction (MBSR), a bachelors in human development, and a masters in psychology, and is a certified Mindfulness Meditation teacher. As the MBSR coordinator at our site, she can answer questions about the MBSR program and can help you learn how to better manage pain and other chronic symptoms.
Sharzad is also a mother of two, a former school psychologist, and teaches bilingual preschoolers through music and dance on her off days. She is an alumni of UC San Diego, and Cal State Northridge. She loves yoga, singing, learning about mindfulness, reading, and finding many variations of the same song. Figure skating and basketball are her favorite sports to watch, though she is not great at either. Sharzad also enjoys a variety of TV and movie fandoms, including Avengers, Star Wars, Lost, Hamilton, Buffy The Vampire Slayer, and especially Harry Potter. Did we mention she is a Harry Potter fan?!