Clinical Pearls & Morning Reports
Published September 22, 2021
Juvenile idiopathic arthritis is a broad term that encompasses a heterogeneous group of disorders. The International League of Associations for Rheumatology (ILAR) classification system describes seven types: oligoarticular arthritis, polyarticular arthritis (rheumatoid factor–positive and rheumatoid factor–negative), enthesitis-related arthritis, psoriatic arthritis, undifferentiated arthritis, and systemic arthritis. Read the NEJM Case Records of the Massachusetts General Hospital here.
Q: Is systemic juvenile idiopathic arthritis a common form of juvenile idiopathic arthritis?
A: Systemic arthritis is one of the least common and most severe types. It accounts for 5 to 15% of new diagnoses of juvenile idiopathic arthritis in North America and Europe.
Q: Systemic juvenile idiopathic arthritis most often develops in children of what age?
A: Systemic arthritis most often develops in children younger than 5 years of age, although it occurs at all ages. Unlike other types of juvenile idiopathic arthritis, systemic arthritis is seen just as often in boys as in girls. Most children with other types of juvenile arthritis receive the diagnosis in the outpatient clinic, but children with systemic arthritis are quite ill and are usually evaluated in the hospital setting.
A: Systemic juvenile idiopathic arthritis is a clinical diagnosis that is made after all other causes have been ruled out. The fever characteristically occurs on a daily basis, with high spikes in temperature once or twice a day. The rash is described as an evanescent, salmon-colored, macular rash that is most apparent when the temperature is high. The arthritis is usually polyarticular and can involve large and small joints. Unfortunately, many patients do not meet all the ILAR diagnostic criteria. The fever pattern and rash can be atypical, and the arthritis may not appear for weeks or even months after the onset of disease. Laboratory abnormalities associated with the illness are not specific and include leukocytosis, neutrophilia, anemia, thrombocytosis, and elevations in the erythrocyte sedimentation rate and levels of C-reactive protein, d-dimer, and ferritin. Autoantibodies such as rheumatoid factor, cyclic citrullinated peptide, antineutrophil cytoplasmic antibody, and antinuclear antibody are generally not found. Most patients who ultimately receive a diagnosis of systemic juvenile idiopathic arthritis have undergone an extensive workup to rule out alternative causes such as infection, cancer, inflammatory bowel disease, and other rheumatic diseases, including Kawasaki’s disease and polyarteritis nodosa.
A: In the past, treatment consisted of glucocorticoids, often administered at high doses, accompanied by disease-modifying antirheumatic drugs such as methotrexate. With the advent of biologic agents and continued research into the cytokine profile associated with systemic juvenile idiopathic arthritis, treatment has evolved over the past decade. The interleukin-1 inhibitors anakinra, canakinumab, and rilonacept and the interleukin-6 inhibitor tocilizumab have proven very effective in treating this condition and may help to minimize or shorten the duration of glucocorticoid use. Outcomes in patients with systemic juvenile idiopathic arthritis can vary. Although 40% of patients have a monophasic course with disease remission, and a small percentage of patients have a polyphasic course with periods of active disease and periods of quiescence, over half of patients have ongoing arthritis even if the systemic features have subsided. All patients with systemic juvenile idiopathic arthritis need to be monitored for worsening of disease and for the development of macrophage activation syndrome, a severe complication that can occur in up to 10% of patients. Macrophage activation syndrome is characterized by fever, hepatic dysfunction, purpura, and involvement of the central nervous system and can lead to multiorgan failure.