Autoimmune diseases are conditions where the body’s immune system, which normally protects us from harmful invaders like bacteria and viruses, mistakenly attacks its own healthy tissues. This can happen in many parts of the body, but one of the most common and painful effects is joint pain. Many people with autoimmune diseases such as rheumatoid arthritis, lupus, and others experience swelling, stiffness, and pain in their joints, sometimes making it hard to move or even do simple tasks like opening a jar or walking up stairs. To understand why this happens, it’s important to look at how the immune system works and what goes wrong in autoimmune diseases.
The immune system is like a security team for the body. It is designed to recognize and destroy anything that doesn’t belong, such as germs or damaged cells. When the immune system is working properly, it can tell the difference between foreign invaders and the body’s own cells. But in autoimmune diseases, this system gets confused. Instead of protecting the body, it starts attacking healthy tissues, including the joints. This attack leads to inflammation, which is the body’s natural response to injury or infection. Inflammation is usually helpful because it brings healing cells to the site of damage, but when it happens in the wrong place or for too long, it can cause pain and damage.
In the case of joint pain, the immune system targets the lining of the joints, which is called the synovium. The synovium is a thin layer of tissue that surrounds the joint and produces fluid to help the joint move smoothly. When the immune system attacks the synovium, it becomes inflamed and swollen. This inflammation can cause the joint to feel warm, look red, and become painful. Over time, if the inflammation continues, it can damage the cartilage and bone inside the joint, leading to more pain and stiffness. This is why people with autoimmune diseases often have joints that are not only painful but also stiff and sometimes deformed.
One of the main reasons autoimmune diseases cause joint pain is because of the way immune cells behave in these conditions. In rheumatoid arthritis, for example, certain immune cells called T cells become overactive and start attacking the joint tissues. This overactivity is linked to changes in the way these cells use energy and process nutrients. Research has shown that a protein called ABHD11 plays a key role in these metabolic changes. When ABHD11 is active, it helps drive the overactivity of T cells, leading to more inflammation and joint damage. When ABHD11 is blocked or inhibited, the metabolic changes that cause inflammation are reduced, which can help lessen joint pain and swelling. This discovery has opened up new possibilities for treatments that target ABHD11 to help people with autoimmune diseases [1].
Another important factor in joint pain is the role of other immune cells and molecules. In rheumatoid arthritis, for example, the immune system produces proteins called cytokines, which are signaling molecules that help coordinate the immune response. Some of these cytokines, like tumor necrosis factor (TNF) and interleukin-6 (IL-6), are known to promote inflammation and contribute to joint pain. When these cytokines are present in high levels, they can cause the synovium to thicken and produce more fluid, leading to swelling and pain. Treatments that block these cytokines, such as TNF inhibitors, have been shown to reduce joint pain and inflammation in many people with autoimmune diseases [3].
The complement system, which is another part of the immune system, also plays a role in joint pain. The complement system is a group of proteins that help the immune system destroy invaders and clear away damaged cells. In autoimmune diseases, the complement system can become overactive and contribute to inflammation in the joints. For example, the protein C5a, which is part of the complement system, has been shown to promote inflammation and joint damage in rheumatoid arthritis. Blocking C5a or other parts of the complement system has been explored as a potential treatment for autoimmune diseases, although more research is needed to fully understand its effects [3].
In addition to these immune system factors, there are also genetic and environmental influences that can make someone more likely to develop autoimmune diseases and joint pain. Some people have genes that make their immune system more prone to attacking healthy tissues, while others may be exposed to environmental triggers like infections, stress, or certain chemicals that can set off an autoimmune response. These factors can interact in complex ways to increase the risk of developing joint pain and other symptoms of autoimmune diseases [3].
The experience of joint pain in autoimmune diseases can vary from person to person. Some people may have mild pain and stiffness that comes and goes, while others may have severe pain and swelling that affects their daily life. The pain can be worse in the morning or after periods of inactivity, and it may improve with movement or exercise. In some cases, joint pain can lead to other complications, such as damage to the cartilage and bone, which can make it harder to move and increase the risk of disability. Managing joint pain in autoimmune diseases often involves a combination of medications, lifestyle changes, and physical therapy to help reduce inflammation and improve joint function [4].
Medications used to treat joint pain in autoimmune diseases include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, disease-modifying antirheumatic drugs (DMARDs), and biologic agents. NSAIDs help reduce pain and inflammation, while corticosteroids can quickly reduce swelling and pain. DMARDs and biologic agents work by targeting the underlying immune system processes that cause inflammation and joint damage. These treatments can be very effective for many people, but they may also have side effects and require careful monitoring by a healthcare provider [4].
Lifestyle changes can also play an important role in managing joint pain. Regular exercise, a healthy diet, and stress management can help reduce inflammation and improve overall well-being. Physical therapy can help strengthen the muscles around the joints and improve flexibility, which can make it easier to move and reduce pain. In some cases, assistive devices like braces or splints may be helpful to support the joints and reduce strain [4].
In summary, autoimmune diseases cause joint pain by triggering the immune system to attack healthy tissues in the joints, leading to inflammation, swelling, and damage. This process involves a complex interplay of immune cells, proteins, and metabolic changes, as well as genetic and environmental factors. Understanding these mechanisms has led to the development of new treatments that target specific parts of the immune system to help reduce joint pain and improve quality of life for people with autoimmune diseases.
Sources
[1] Inside Precision Medicine. Key Protein Driving Autoimmune Inflammation Identified. https://www.insideprecisionmedicine.com/topics/patient-care/key-protein-driving-autoimmune-inflammation-identified/
[2] All Imm. Exploring genetic linkage between rheumatoid arthritis and systemic … https://www.all-imm.com/index.php/aei/article/view/1492/2137
[3] PMC. Regulation of the innate immune response in rheumatoid arthritis. https://pmc.ncbi.nlm.nih.gov/articles/PMC12621325/
[4] Cleveland Clinic. Lupus: What It Is, Symptoms, Causes & Treatment. https://my.clevelandclinic.org/health/dise
