[Neuraminidase-producing pneumococci in the pathogenesis of hemolytic-uremic syndrome]

Hemolytic-uremic syndrome (HUS) accompanied by pneumococcal infections forms a characteristic subgroup of HUS. Pneumococcal neuraminidase splits off neuraminic acid from the glycoproteins present on the surface of red cells, thrombocytes and endothelial cells, and thus exposes the hidden Thomsen cryptantigen (T-Ag). The T-Ag can then react with a complement-fixing antibody of the IgM class which is present in all human plasmas after the age of 6 months. Early diagnosis of T-transformation should be attempted. Highly suggestive hints are: pneumonia, hemolytic anemia, reticulocytopenia, difficulties in ABO typing, a positive direct Coombs test and a positive minor cross-match. The definite diagnosis of T-transformation is established with the aid of anti-T agglutinins from Arachis hypogaea, the common peanut. Two children aged 19 and 22 months with pneumonia, Coombs-positive hemolytic anemia, HUS and exposure of the T-Ag on the red cell membrane are described. In one of them, circulating neuraminidase and circulating pneumococcal antigen of serotype 3 were found. In both children exchange transfusions resulted in elimination of circulating neuraminidase and of T-transformed red cells prone to hemolysis.