Are There Different Types of RA?
My rheumatologist believes that I may have a combination of rheumatoid arthritis (RA) and ankylosing spondylitis (AS). I present classic symptoms of RA including joint inflammation and damage in joints commonly associated with RA, symmetrical presentation on both sides of the body, bone erosion, duration of the symptoms, positive blood tests associated with RA, and fatigue. At the same time my rheumatologist noted limited spinal mobility and many problems with my ankles and Achilles’ tendons that are common with ankylosing spondylitis. My first autoimmune symptom, which occurred years before joint problems surfaced, was inflammatory uveitis (iritis) in both eyes. An ophthalmologist immediately suspected ankylosing spondylitis and asked about my back and hip joints - which surprised me! While Achilles tendon problems and uveitis can be associated with RA, they are more commonly seen in ankylosing spondylitis patients. But a blood test for HLA-B27, a common genetic test related to ankylosing spondylitis, was negative. The official diagnosis in my medical chart has always been rheumatoid arthritis (diagnostic code 714).
Diagnosing RA is not always a straightforward process. There are many people with clinical symptoms of RA who do not have a positive blood test. Such patients may be called “seronegative” and upwards of 30% of cases are classified as such (Duskin & Eisenberg, 2010). This lack of completely accurate blood tests adds fuel to the argument that there may be different types of RA.
Muddying the water is the fact that treating RA involves a slew of medications that work in varying capacities depending on the patient and treatment combination. While many RA patients find relief from the most common treatments like methotrexate, Enbrel, and Humira, they are not effective for up to 30-40% of patients (Rubbert-Roth & Finckh, 2009). Personally, I have been through a slew of RA treatments, four DMARDs and seven biologics, in an effort to find a combination that works for the long term.
There are different types of inflammatory arthritis including rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis (Arthritis Research UK). Even young children can get inflammatory arthritis. While it used to be called Juvenile RA, it’s now called juvenile idiopathic arthritis (JIA). There are even sub-types of JIA. And each of these diseases presents different clinical patterns and blood tests. All of these related diseases are treated with similar medications.
The scientific community agrees that RA is not a clear cut, singular disease. According to researchers from the Netherlands, “Rheumatoid arthritis (RA) is a heterogeneous disease with unknown cause“ (van der Pouw Kraan, et al., 2007). These researchers found differences in the genetic expressions of RA patients lending some credence to a genetic link to sub-types of RA. In an earlier study of the genetics of RA, researchers found that a gene called HLA-DR was found in 83% of patients with classical or definite RA (Woodsworth, et al., 1989). But no explanation is given for the 17% of RA patients who did not show this gene. In 2010, a group of researchers found four genetic sub-types of RA (Dennis, et al., 2010). Furthermore, Japanese scientists found genetic differences in RA patients at the molecular level adding credence for subsets of the disease (Ishihara & Igarashi, 2012). Some researchers even found different emotional responses in RA patients (Tillmann, et al., 2010.
While the causes of RA are not completely evident, most scientists suspect a combination of factors including genetic and environmental causes. Scientists are now beginning to unravel the complexities of RA and find that there may actually be a variety of sub-types of the disease. I predict that future research into RA and other autoimmune diseases will reveal that genetics and environmental factors impact the way individuals present symptoms and respond to treatments. This knowledge may lead to definitions of RA sub-types and better treatments in the future.
How does your pet support your RA journey?