To assess the frequency of Streptococcus pyogenes in children with early arthritis, compare the characteristics in patients with post-streptococcal ReA (PSReA) with those in patients with other types of arthritis, and describe the occurrence of carditis in PSRA.
In a population-based Norwegian study, the physicians were asked to refer all children with suspected arthritis. The arthritis patients were followed up at 6 weeks, 6 months and 18 months. The presence of S. pyogenes was based on throat smear or antibodies. Echocardiography was performed in the patients with ARF or PSRA.
Thirty-two (18%) of the 173 children with arthritis tested positive for S. pyogenes. The percentage of positive tests rose steadily with age and peaked at ages 8-11 (35%). Six weeks after admission arthritis was present in 33% of the PSRA patients, which was less frequent than in the juvenile idiopathic arthritis (JIA) patients (P < 0.001), but more frequent than in the transient arthritis patients (P = 0.012). Hip arthritis was more frequent and knee/ankle arthritis, ANA and HLA-B27 were less frequent in PSRA than in JIA (P < 0.001, P = 0.009 and P = 0.029, respectively). The PSRA patients were older than those with transient arthritis (P = 0.007). One child with ARF had carditis.
Streptococcus pyogenes was present in 18% of children with arthritis. The patient characteristics, clinical presentation and early disease course in PSRA was different from that of JIA and transient arthritis.