Psoriatic arthritis is a chronic autoimmune disease that primarily affects the joints and the places where tendons and ligaments attach to bones. It is closely linked to psoriasis, a skin condition characterized by red, scaly patches, but psoriatic arthritis involves inflammation that extends beyond the skin to the musculoskeletal system. This inflammation causes joint pain, swelling, stiffness, and can lead to joint damage over time.
At its core, psoriatic arthritis occurs because the immune system, which normally protects the body from infections, mistakenly attacks healthy tissues, particularly the joints and skin. This immune system malfunction triggers inflammation, which is the body’s natural response to injury or infection but becomes harmful when it is chronic and misdirected. The inflammation in psoriatic arthritis affects the synovium—the lining of the joints—leading to swelling and pain. It can also inflame the entheses, which are the sites where tendons and ligaments connect to bones, causing a condition called enthesitis.
The joints most commonly affected include those in the fingers and toes, which can become swollen and take on a sausage-like appearance known as dactylitis. Psoriatic arthritis can affect any joint in the body, including the spine, knees, ankles, and feet. Unlike some other types of arthritis, psoriatic arthritis often affects only one side of the body or a few joints asymmetrically. The inflammation causes the joints to feel warm, tender, and stiff, especially after periods of inactivity such as in the morning or after sitting for a long time.
Over time, the persistent inflammation can damage cartilage and bone within the joint, leading to deformities and loss of function. This damage can make movement painful and difficult, impacting daily activities and quality of life. In some cases, psoriatic arthritis progresses rapidly, causing severe joint damage within a short period, while in others, symptoms may be mild and progress slowly.
The exact cause of psoriatic arthritis is not fully understood, but it is believed to result from a combination of genetic and environmental factors. People with a family history of psoriasis or psoriatic arthritis are at higher risk. Environmental triggers such as infections, physical trauma, or stress may initiate the disease in genetically predisposed individuals by activating the immune system abnormally.
Symptoms of psoriatic arthritis can vary widely. Joint pain, swelling, and stiffness are common, but people may also experience fatigue and skin symptoms like psoriasis plaques. The disease often follows a pattern of flares and remissions, where symptoms worsen for a time and then improve or disappear temporarily. During flares, joint pain and swelling intensify, and new symptoms may appear.
Psoriatic arthritis can also affect the feet, causing pain and stiffness in the toes and ankles. This can make walking difficult and may require assistive devices during severe flares. The inflammation can extend beyond the joints to involve tendons and ligaments, causing additional pain and swelling.
Diagnosis of psoriatic arthritis involves a combination of clinical evaluation, medical history, physical examination, and imaging studies such as X-rays or MRI to assess joint damage and inflammation. Blood tests may be used to rule out other types of arthritis but there is no single test that definitively confirms psoriatic arthritis.
Treatment focuses on reducing inflammation, relieving symptoms, preventing joint damage, and improving quality of life. This often involves medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs), and biologic agents that target specific parts of the immune system. Physical therapy and lifestyle changes, including exercise and stress management, also play important roles in managing the disease.
Living with psoriatic arthritis means managing a condition that can affect both the skin and joints in complex ways. The unpredictable nature of flares and remissions requires ongoing monitoring and adjustment of treatment to maintain joint function and control symptoms. Early diagnosis and treatment are crucia