Various rheumatic syndromes in adult patients associated with high antistreptolysin O titres and their differential diagnosis with rheumatic fever.

OBJECTIVES The purpose of this study was to analyse retrospectively adult patients with acute joint or muscle symptoms and a high antistreptolysin O (ASO) titre to find out which syndromes of clinical arthritis are associated with serological evidence of streptococcal infection. METHODS Seventy six adult patients with an acute arthritis syndrome or an exacerbation in their chronic rheumatic disease and simultaneously a high ASO titre (> or = 500 Todd units) were examined in two time periods in the 1980s. RESULTS Twenty six patients had arthritis associated with a known rheumatic disease, 25 had non-specific arthralgia/myalgia, 20 had reactive arthritis, and five had septic arthritis. No case of classic rheumatic fever classified by two major criteria was found. Six patients fulfilled one major and at least two minor criteria. The frequency of HLA-B27 was significantly higher in the whole patient group than in the healthy Finnish population (30 v 14%). CONCLUSIONS It is concluded that classic rheumatic fever is now rare, even in patients with arthritis with a high ASO titre. These results support the suggestion that beta haemolytic streptococci may trigger reactive arthritis as well as rheumatic fever.