OSLO, Norway—A population-based Norwegian study of recent-onset childhood arthritis showed that a significant number of these cases are associated with Streptococcus pyogenes infection, that these cases have distinctly different time courses from either juvenile idiopathic arthritis (JIA) or transient arthritis, and that  poststreptococcal reactive arthritis (PSRA) patients probably do not need routine cardiology follow-up. Oystein Riise, MD, of the department of rheumatology at Rikshospitalet Medical Centre, in Oslo, Norway, reported the study in the early online edition of Rheumatology.¹

“In this study, the percentage of positive streptococcal tests correlated with the age of the child and was found in 35% of the arthritis patients aged 8 to 11 years. Patients with PSRA were older and had longer disease duration than those with transient arthritis. Hip involvement, inactive disease at 6 weeks and 6 months, and negative antinuclear antibody (ANA) and HLA-B27 were more frequent in PSRA than in the JIA patients. One-third of the patients with PSRA still had signs of streptococcal infection after 18 months. Carditis was only found in one child, who had acute rheumatic fever (ARF),” Dr. Riise said.  

Dr. Riise and colleagues conducted a population-based, multicentre study in three counties in Norway, with a total population of 1,252,835, of whom 255,303 were under age 16. All primary care physicians were asked every third month for 1 year to refer all children with possible or evident recent-onset arthritis to the appropriate hospital on the day the patient was first seen. Inclusion criteria included presence of arthritis, residence in one of the participating counties, age <16 years on admission, and test performed for S. pyogenes. Arthritis diagnosis required either swelling of a joint, restricted mobility of a joint with warmth and/or tenderness or pain, or arthritis demonstrated by ultrasound or by magnetic resonance imaging (MRI).

Patients were examined on admission, at 6 weeks, and at 6 months. The PSRA patients were additionally examined at 18 months. Swollen, tender, and mobility-restricted joint counts and history of joint pain were recorded at each visit.

All PSRA patients were tested with standard 12-lead electrocardiogram and 2-D and Doppler echocardiography at the 18-month follow-up visit. Patients with ARF had a cardiac assessment during the first weeks after admission and were followed yearly by a pediatric cardiologist.

The researchers found that 217 patients met the criteria for arthritis and that 173 also had been tested for S. pyogenes. These 173 children form the basis for this report. Their median age was 4.9 years, and they had a median symptom duration of 3 days upon admission.

Of the 173 children with arthritis, 32 (18%) were positive by streptococcal smear and/or serology. Median age for those who tested positive was 6.3 years versus 4.7 years for the group as a whole (P = .003).

“The percentage of children who tested positive for streptococci increased steadily with age up to a peak of 35% at 8 to 11 years, after which it dropped to 21% in children aged 12 to 15. The percentage of patients with a positive throat swab peaked to 20% at 6 to 7 years, and no positive throat swab was found in the patients aged 12 to 15 years,” Dr. Riise said.

Patients with JIA had longer duration of arthritis symptoms than those with PSRA (median 20 days versus 3 days, P = .002). Those with transient arthritis were more likely to have had a respiratory tract infection during the 4 weeks before admission than those with PSRA (84% versus 33%, P = .002).

The PSRA patients were more likely to have hip arthritis and less likely to have knee or ankle arthritis than those with JIA, and involvement of other joints was less common in the PSRA patients than in those with JIA.

“Six weeks after admission, active arthritis was still present in 33% of the PRA patients, which was less frequent than in the JIA patients (91%, P <.001), but more frequent than in the transient arthritis patients (10%, P = .012),” Dr. Riise said.

None of the PSRA patients had any signs of cardiac involvement. One of the two children with ARF had carditis.

Translating research into practice

“A review of recent studies has shown that 4 of 88 children with PSRA develop carditis. Although our sample is small, our data do not support that all Norwegian children with arthritis who test positive for S. pyogenes should be followed up by a cardiologist. However, this may not apply to PSRA patients in other geographical areas, especially those where ARF and carditis are common,” Dr. Riise said.

Reference

1. Riise OR, Lee A, Cvancarova M, et al. Recent-onset childhood arthritis—association with Streptococcus pyogenes in a population-based study. Rheumatology 2008; [Epub ahead of print] April 17, 2008; doi:10.1093/rheumatology/ken122