Among the different types of inflammatory rheumatism, we can cite rheumatoid arthritis (RA) which refers to inflammation and swelling of at least 3 joints (poly), as well as pseudo-polymyalgia rheumatica (PPR). These two rheumatisms have points in common but also a certain number of differences. Professor Jérôme Avouac, rheumatologist at Cochin Hospital and Teacher-Researcher at the University of Paris and the Cochin Institute, explains which ones to us.
What is polymyalgia rheumatica? Definition
“There polymyalgia rheumatica (PMR) is not polyarthritis strictly speaking. This is a periarticular inflammation (at the periphery of the inflammation) related to the disease. informs Professor Jérôme Avouac‚ rheumatologist at the Cochin Hospital and Teacher-Researcher at the University of Paris and the Cochin Institute. It is the structures around the joint that are inflamed and not the joints themselves. This is why we use the term pseudo-polyarthritis.
What do rheumatoid arthritis and polymyalgia rheumatica have in common?
These are two rheumatological diseases managed by rheumatology doctors. These are also two diseases in which there is local and systemic inflammation, that is to say detected in the blood of patients. “They also have the common point of responding well to corticosteroids,” informs Professor Jérôme Avouac. Corticosteroids are used to treat a flare-up of rheumatoid arthritis or to treat pseudo-polyarthritis rheumatica as first-line treatment. THE methotrexate (immunosuppressant) and biotherapies (commeletocilizumab) are also used in the treatment of these two pathologies.
Age and sex: the big difference between rheumatoid arthritis and polymyalgia rheumatica
Rheumatoid arthritis occurs in younger people than polymyalgia rheumatica. “It most often begins between the ages of 40 and 50, while pseudo-polyarthritis always occurs after the age of 50 and mainly affects older people around the age of 65-70,” informs Professor Jérôme Avouac. Both diseases mainly affect women but the sex ratio is higher for rheumatoid arthritis (3 women for 1 man vs. 2 women for 1 man). Rheumatoid arthritis is the most common inflammatory rheumatism in France. Pseudo-polyarthritis rheumatica is rarer. “Cases of pseudo-polymyalgia rheumatica have been described after a vaccine against SARS-COV2 or after cancer immunotherapy”, specifies the rheumatologist interviewed.
Weight loss, fatigue, pain… what are the symptoms of these inflammatory rheumatisms?
These two diseases also do not affect the same joints. Rheumatoid arthritis mainly affects the small joints of the hands and feet through arthritis, while pseudo-polyarthritis affects the scapular girdle (the shoulders) and the pelvic girdle (the pelvis). “This is bursitis‚ inflammation of the bursae which are on the periphery of the gluteus medius for the pelvis or at the level of the shoulder (subacromial bursitis). Other differences between these two inflammatory rheumatisms: pseudo-polyarthritis rhizomelic s accompanies a deterioration in general condition: weight loss‚ fatigue.”
This disease can sometimes be associated with cancers, especially when patients do not respond well to corticosteroid therapy: these are paraneoplastic pseudo-polyarthritis. Pseudopolymyalgia rheumatica (PMR) can also be associated with Horton’s disease‚ an inflammatory disease of the vessels.
Rheumatoid arthritis and pseudo-polyarthritis rhizomelic: how do we tell the difference?
The populations affected by these two rheumatological diseases being different‚ are not often faced with doubts about the diagnosis‚ except in a certain case. : “In older patients‚ rheumatoid arthritis can start in the shoulders‚ before affecting the hands‚ which then resembles pseudo-polyarthritis,” underlines the specialist interviewed. Rheumatoid arthritis is an autoimmune disease. We will therefore find autoantibodies (rheumatoid factors, anti-CCP antibodies) in the blood whereas pseudo-polyarthritis rheumatica is an inflammatory disease but non-autoimmune.
The detection of antibodies through a blood test‚ the clinical presentation (arthritis for RA‚ rather bursitis for PPR) and also and above all the radiographic examination will make it possible to make the diagnosis. “RA damages the joints. On x-rays we will see erosions and pinching of the joint spaces. PPR, on the other hand, does not damage the joints“, explains Professor Jérôme Avouac. He specifies that ultrasound is also very useful to differentiate between these two rheumatological diseases: “This allows us to see joint effusions which are a sign of rheumatoid arthritis or bursitis in pseudo-polyarthritis rheumatica.” THE PET scanner can be used in the case of PMR to map the lesions around the joints‚ to see if there is associated Horton’s disease (inflammation of the vessels) and to check that there is no presence of image suspected of a tumor.
Treatments: differences in medical monitoring between rheumatoid arthritis and pseudo-polyarthritis rheumatica
The management of these two diseases is different‚ even if the same medications are used. “Rheumatoid arthritis is a chronic disease while polymyalgia rheumatica can be cured with treatment,” explains the doctor interviewed. PMR can be treated only with corticosteroids and benefit from basic treatment in the event of corticosteroid resistance. “RA‚ requires basic treatment (Methotrexate‚ biotherapy)”, indicates Professor Jérôme Avouac.