Juvenile spondyloarthritis (JSpA) is a group of inflammatory rheumatic diseases that begin in childhood before age 16. This arthritis is characterized by inflammation in the joints and where tendons and ligaments attach to bone (entheses). JSpA primarily affects the lower body, including the pelvis, hips, and knees, and can also involve the spine.
As a form of juvenile idiopathic arthritis, its specific cause is unknown. It represents a spectrum of diseases rather than a single diagnosis. The course varies, as some children experience mild symptoms while others face a persistent condition that continues into adulthood.
Recognizing the Symptoms
A primary symptom of JSpA is inflammatory back pain. This discomfort is most severe at night or after rest, like upon waking, and improves with physical activity. In some cases, children adopt a stooped posture to alleviate the pain.
Enthesitis, inflammation where tendons and ligaments connect to bone, is a common feature of JSpA. It causes pain and tenderness at sites like the heel, the sole of the foot, and around the kneecap. This symptom is often one of the first to appear.
JSpA also frequently involves peripheral arthritis, the inflammation of large joints. This affects the lower extremities, causing pain, warmth, and swelling in the knees, ankles, and hips. In children, this lower-body joint involvement is often a more prominent early symptom than the back pain that is more characteristic in adults with the disease.
Some children with JSpA may also experience symptoms outside of the joints. A potential complication is uveitis, or inflammation of the eye, which can cause eye pain, redness, and sensitivity to light. Other issues include skin conditions like psoriasis or gastrointestinal problems similar to those seen in inflammatory bowel disease.
Understanding the Causes
The cause of JSpA is not fully understood but is considered multifactorial, involving genetic and environmental factors. The underlying mechanism is autoimmune, where the immune system mistakenly attacks healthy tissues in the joints and entheses.
A strong genetic component is linked to the human leukocyte antigen B27 (HLA-B27) gene. A large percentage of individuals diagnosed with spondyloarthritis carry this gene. However, having the HLA-B27 gene does not mean a person will develop the condition, as many people with the gene never experience arthritis.
An environmental trigger, such as a bacterial infection, may be necessary to activate the disease in genetically predisposed individuals. An infection might set off an immune response that fails to shut down properly and instead targets the musculoskeletal system.
The Path to Diagnosis
Diagnosing JSpA can be complex because symptoms are often episodic. The process begins with a pediatric rheumatologist, who will conduct a thorough medical history and physical examination. The doctor will ask about the child’s symptoms and any family history of related conditions, while the physical exam checks for joint swelling, tenderness, and signs of enthesitis.
To support clinical findings, physicians use blood tests to look for general markers of inflammation. Common tests include the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which are elevated when inflammation is present. A blood test to detect the HLA-B27 gene is also a standard part of the workup.
Imaging studies are another component of the diagnostic process. X-rays may be ordered to look for changes in the joints, particularly the sacroiliac joints at the base of the spine. However, X-rays may not show evidence of inflammation in the early stages, so a magnetic resonance imaging (MRI) scan is often used. An MRI is more sensitive and can detect early inflammation in joints and entheses before permanent damage occurs.
Managing and Treating JSpA
The goals of managing JSpA are to control inflammation, alleviate pain, maintain joint function, and prevent long-term damage. A treatment plan includes physical and occupational therapy. These therapies are used to teach exercises that strengthen muscles, improve posture, and preserve the range of motion in affected joints.
Medication is a primary part of the treatment strategy, with several types used to manage symptoms and prevent damage:
- Nonsteroidal anti-inflammatory drugs (NSAIDs), such as naproxen or ibuprofen, are often the first medications used to reduce pain and inflammation.
- Corticosteroid injections directly into a specific joint space can provide rapid relief for arthritis localized to one area, such as a knee or ankle.
- Disease-modifying antirheumatic drugs (DMARDs), like sulfasalazine or methotrexate, may be prescribed if NSAIDs are not sufficient to control the arthritis and prevent joint damage.
- Biologic agents are advanced, targeted therapies for more severe cases. These drugs, such as TNF inhibitors, work by blocking specific proteins in the immune system that drive inflammation.