Is there an association between rheumatoid arthritis and systemic lupus erythematosus (lupus)? Can someone have both diseases or must he or she be diagnosed with only one? What are the challenges in addressing these questions and more?
From a recent article published in the journal Arthritis Research & Therapy, the average RA patient has 1.6 comorbidities and that number increases with the patient's age. There is increasing interest in the field of comorbidity (the existence of more than one disease in a person, usually independently of one another) and rheumatic diseases.
"The past decade has also brought new insights regarding the comorbidity associated with rheumatic diseases. Strong evidence now shows that persons with RA are at a high risk for developing several comorbid disorders, that these conditions may have atypical features and thus may be difficult to diagnose, and that persons with RA experience poorer outcomes after comorbidity compared with the general population. Taken together, these findings underscore the complexity of the rheumatic diseases and highlight the key role of epidemiological research in understanding these intriguing conditions."
How are RA and Lupus diagnosed?
The American College of Rheumatology has defined criteria for the diagnosis of rheumatic diseases, including rheumatoid arthritis and lupus. The following lists of criteria were developed in 1987 (for RA) and 1982 (for lupus).
Rheumatoid Arthritis - At least four of seven criteria must be met for diagnosis:
- Morning stiffness of >1 hour most mornings for at least 6 weeks.
- Arthritis and soft-tissue swelling of >3 of 14 joints/joint groups, present for at least 6 weeks
- Arthritis of hand joints, present for at least 6 weeks
- Symmetric arthritis, present for at least 6 weeks
- Subcutaneous nodules in specific places
- Rheumatoid factor at a level above the 95th percentile
- Radiological changes suggestive of joint erosion
Lupus - At least four of eleven criteria must be met for diagnosis:
- Malar rash: butterfly-shaped rash across cheeks and nose
- Discoid (skin) rash: raised red rashes that scar
- Photosensitivity: skin rash as a result of reaction to sunlight
- Mouth or nose ulcers: usually painless
- Nonerosive Arthritis (bones around joints do not get destroyed): in 2 or more joints with tenderness, swelling, or effusion
- Cardio-pulmonary involvement: inflammation of the lining around the heart (pericarditis) and/or lungs (pleuritis)
- Renal (kidney) disorder: excessive protein in the urine (proteinuria), or cellular casts in the urine
- Seizures or other neurologic disorder
- Hematologic (blood) disorder: low red blood cell count (hemolytic anemia), lower white blood cell count (leukopenia), or low platelet count (thrombocytopenia)
- Immunologic disorder: antibodies to doubled stranded DNA, antibodies to Sm, positive antiphospholipid antibody such as anticardiolipin, or false positive syphillis test (VDRL)
- Antinuclear antibodies (ANA): positive test in absence of drugs known to induce it
- Not on the list of criteria, but common symptoms: fever, fatigue, weight loss, and hair loss
Incidence of Co-morbidity of RA and Lupus?
The Lupus Foundation of America states that the majority of people with lupus have lupus alone. However, between 5 and 30 percent of people with lupus report having overlap symptoms -- symptoms of more than one disease. The likelihood of a person with lupus also having an overlap disease is 15 percent, distributed as follows: Rheumatoid Arthritis (1%), Polymyositis-Dermatomyositis (2%), Mixed Connective Tissue Disease (3%), Scleroderma (4%), and Sjogren's syndrome (5%). There are at least 1.5 million Americans living with lupus, thus statistically approximately 15,000 may have both Lupus and RA.
"In lupus, joint pain (arthralgia) is common. Joint swelling (arthritis) may be present in some cases, but the majority of those with lupus experience joint pain without swelling or only intermittent swelling. In rheumatoid arthritis (RA), joint swelling is always present and pain is common but less prominent. Because rheumatoid arthritis is more likely than lupus to cause joint deformities and bone destruction, joint replacement or reconstructive surgery is more often required in RA than in SLE. If a person with lupus develops severe arthritis with joint deformities, he/she should be considered to have rheumatoid-like arthritis. In some instances, the physician might have reason to believe that both diseases -- SLE and RA -- have occurred in the same person. When arthritis develops in the course of lupus, treatment with non-steroidal anti-inflammatory drugs (NSAIDs), low doses of cortisone, and the antimalarial drug hydroxychloroquine (Plaquenil) are usually helpful. People with lupus who have typical rheumatoid arthritis are prescribed the standard forms of RA treatment. These include methotrexate, sulfasalazine and in some cases, more potent drugs to suppress joint inflammation."
Since both RA and lupus can cause joint pain, with swelling and tenderness, an accurate diagnosis may be more difficult. Published in The Journal of Rheumatology, a study of 603 patients diagnosed with rheumatoid arthritis showed that 15.5% of patients exhibited four or more features of lupus after 25 years post-RA diagnosis. Those patients who developed more than 4 lupus features, including proteinuria and thrombocytopenia, had an increased risk of death. The conclusion of the study was that lupus features were common in RA given sufficient observation time.
The Arthritis Foundation estimates that 1.3 million Americans have rheumatoid arthritis. Combine that statistic with the above study, appropriately 200,000 of those may develop four or more features of Lupus over a long period of time. Does that mean they qualify for being diagnosed with Lupus? The study abstract did not explain further.
Possible Genetic Connection
An interesting research study, published in the New England Journal of Medicine (2007), identified a genetic variation that increases the risk of rheumatoid arthritis (RA) and systemic lupus erythematosus (lupus). According to the press release, these research findings result from a long-time collaboration between the Intramural Research Program (IRP) of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) and other organizations. NIAMS is part of the National Institutes of Health.
One variant form of the gene was present at a significantly higher frequency in RA patient samples from the North American Rheumatoid Arthritis Consortium (NARAC) as compared with controls. The scientists replicated that result in two independent collections of RA cases and controls.
The researchers also found that the same variant of the STAT4 gene was even more strongly linked with lupus in three independent collections of patients and controls. Frequency data on the genetic profiles of the patients and controls suggest that individuals who carry two copies of the disease-risk variant form of the STAT4 gene have a 60 percent increased risk for RA and more than double the risk for lupus compared with people who carry no copies of the variant form. The research also suggests a shared disease pathway for RA and lupus.
Can I have RA and Lupus?
Yes, it is possible to have both RA and Lupus, however rare the occurrence. The challenge in diagnosing either disease is that there are no definitive tests and some of the symptoms overlap. Patients will need a rheumatologist for diagnosis and to oversee treatment. Fortunately many of the same medications are used to treat each disease, including methotrexate, plaquenil, prednisone, etc.
What should I do if I have both RA and Lupus?
Much of what you should do is the same as if you had any autoimmune disease. Take care of your body. Get plenty of rest. Exercise as you can. Eat nutritious food. Work with your rheumatologist to find a treatment routine which is effective for you. Reduce stress, both mental and physical. Protect your joints. Protect your skin and organs. Reduce weight if obese. Stay compliant and attend follow-up appointments. Learn as much as you can about your disease. Be proactive and enjoy life.