Clinical features of the ERA subgroup of Juvenile Idiopathic Arthritis
What are the demographic and clinical manifestations of the ERA subgroup of JIA?
The ERA subgroup includes the diseases falling under the umbrella of juvenile spondyloarthropathy, which includes ERA, juvenile ankylosing spondylitis, subsets of juvenile psoriatic arthritis, reactive arthritis, and inflammatory bowel disease-associated arthritis.
• Peak age of onset: 10 to 13 years.
• Gender ratio: male > female 7:1.
• Genetics: HLA-B27 positive in 60% to 80% depending on ethnicity.
• The hallmark of the ERA subgroup is the presence of enthesitis (inflammation at sites of tendon/ligament insertion into bone). The most common sites are patella tendon, Achilles’ tendon, plantar fascia insertions into calcaneous and metatarsal heads, greater trochanter, and tibial tuberosity (may mimic Osgood–Schlatter disease).
• Most frequent joints are the knee, ankle, and midfoot (tarsitis).
• Axial involvement is infrequent at disease onset (only about 24%) but may manifest within 5 to 10 years. Risks for sacroiliitis or spondylitis are HLA-B27 presence, family history of ankylosing spondylitis, male sex, hip arthritis, tarsitis, higher number of active entheses and joint counts at disease onset.
• Extraarticular manifestations:
• Uveitis: acute anterior uveitis in 3% to 7% of patients (see Question 11). Cardiovascular: rare aortic insufficiency can occur.
• Laboratory: ESR elevated; ANA and RF negative.
• Treatment: tailored to predominant manifestations. NSAIDs, intraarticular steroid injections, sulfasalazine, and methotrexate are commonly used for peripheral disease, with use of TNFα inhibitors if disease is refractory. TNF-a inhibitors are indicated when axial disease is present.
• Reactive arthritis and inflammatory bowel disease-associated arthritis can occur and resembles their adult counterparts. Because children may have few abdominal symptoms, any child with iron-deficiency anemia and arthritis should have inflammatory bowel disease in the differential diagnosis.