Arthritis, a common disease that is characterized by inflammation of joints, is composed of more than a 100 different subtypes. Arthritis affects about 54.4 million American adults.
People often consider lupus as an arthritic disease. However, this is untrue. Lupus is not a type of arthritis but instead, inflammatory arthritis is the most common symptom of lupus. Inflammatory arthritis is also a hallmark of rheumatoid arthritis, the most common subtype of arthritis.
Both lupus and rheumatoid arthritis develop due to an impairment in the immune system, and are known as autoimmune diseases. Generally, the immune system plays a role in protecting us from foreign pathogens. However, in some unfortunate circumstances, the immune system becomes dysregulated and starts to attack the body’s own healthy tissue instead, leading to the manifestation of disease.
As mentioned above, arthritis refers to inflammation of the joints leading to joint stiffness and pain. Patients characteristically develop redness and swelling of joints. Patients also tend to suffer from limited range of motion, which prevents full extension and flexion of the joints and is associated with pain, discomfort, and disability. Arthritis develops either due to inflammation (such as from autoimmune disease) or wear and tear of the body’s joints. Some forms of arthritis can also develop due to sports injuries, weight, and occupation that involves repetitive movements.
Lupus is a systemic disease in which the immune system attacks the joints and internal organs such as the heart, lungs, brain, and kidneys. Diagnosis of lupus is most common in people between the ages of 15 and 40. While arthritis is the most common symptom of lupus, it is not the only symptom seen in these patients. People with lupus often develop a characteristic facial rash (often butterfly-shaped), which worsens with sun exposure. Other symptoms include:
- Weakness or fatigue
- Chest pain
- Photosensitivity (sensitivity to the sun’s light)
- Dry eyes
Lupus can also be the cause of serious health issues such as seizures and low red blood cell counts (anemia) and white blood cell counts, the latter of which can weaken the immune system and cause infections. While characteristic symptoms like pain and swelling typically only bother patients during flare-ups, long-term uncontrolled lupus can lead to joint damage that causes symptoms even when the patient isn't experiencing a flare-up. In some cases, lupus will only manifest in one part of the body, but in others, it will spread to other parts.
There are several different types of lupus:
- Systemic lupus erythematosus (SLE)
- Drug-induced lupus
- Cutaneous (discoid lupus)
- Neonatal lupus
Among all types of lupus, SLE is the most frequently diagnosed. Risk factors for SLE include:
- Gender. Women are more frequently diagnosed with SLE compared to men.
- Ethnicity. The disease is more common in African Americans, Asians and those of Hispanic descent.
- Environmental factors
- Certain medications
The link between lupus and arthritis
Studies have shown that there is actually a genetic link between the development of rheumatoid arthritis and lupus. People who have this common genetic link can actually experience features of both these unique diseases. Therefore, many patients have both lupus and rheumatoid arthritis, likely due to the presence of a single gene that causes these diseases.
In particular, studies have identified a gene that lupus and rheumatoid arthritis may be linked to, which is STAT4. This gene is frequently mutated in patients with lupus and/or rheumatoid arthritis. In fact, patients that have a mutated version of STAT4 in their genome are twice as likely to develop lupus compared to individuals with the non-mutated copy of STAT4. Additionally, a mutation in the STAT4 gene also increases the risk of an individual of rheumatoid arthritis by 60 percent.
While researchers are unsure why the STAT4 gene mutates, they do know that mutations in this gene cause a higher risk of developing various autoimmune diseases, including diseases such as juvenile idiopathic arthritis and systemic scleroderma.
Though it is known that STAT4 mutation is connected to the development of autoimmune diseases and serves as a link between lupus and rheumatoid arthritis, there is currently no commercially-available test to check whether you have a mutation in the gene.
Differences between lupus and rheumatoid arthritis
Despite the fact that lupus triggers the development of arthritis, there are major differences between rheumatoid arthritis and lupus-associated arthritis. First, lupus is not erosive while rheumatoid arthritis is. Secondly, lupus arthritis is much less severe compared to rheumatoid arthritis. Third, the primary joints that are affected (including hands, knees, shoulders, elbows, and feet) are different from those affected in rheumatoid arthritis.
Treatments for lupus and rheumatoid arthritis
Unfortunately, at this point, there is no cure for either lupus or rheumatoid arthritis. Both diseases are managed with symptomatic treatment including:
- Nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve inflammation and pain.
- Immunosuppressive drugs, which dampen the immune response.
- Corticosteroids. Injections of corticosteroids into the joints can ease inflammation and reduce pain.
- Physical therapy
Specific treatment for rheumatoid arthritis includes disease-modifying anti-rheumatic drugs (DMARDs).