[Immunologic studies in active rheumatic fever and infectious endocarditis]

We compared clinical and immunological characteristics of acute rheumatic fever (19 cases) and infectious endocarditis (7 cases), because these two diseases can be confused easily with each other and their differential diagnosis is not simple. In this small series we had cases of acute rheumatic fever with splenomegaly and/or vasculitis, as well as infectious endocarditis with subcutaneous nodules, which exemplifies the diagnostic problem. Using laboratory tests we were able to point out differences which are statistically significant, such as: rheumatoid factor by passive agglutination of IgG sensitized latex particles (X2 4.27 p less than 0M05), and tests which reflects the presence of circulating immune complexes, hemolytic capacity of antigammaglobulin antibodies (X2 3.79 p less than 0.05) and the presence of circulating C3 degradation products (X2 5.92 p less than 0.01), which occurs preferentially or exclusively in infectious endocarditis. Although in the standard patient the clinical assessment is usually sufficient to establish a diagnosis, when differentiation between acute rheumatic fever and infectious endocarditis is not clear, immunologic tests are helpful.