A severe case of atypical hemolytic uremic syndrome associated with pneumococcal infection and T activation treated successfully with plasma exchange

A severe nondiarrheal form of hemolytic uremic syndrome in children is associated with pneumococcal infection (pHUS). Neuraminidase released by the pneumococci may cleave N-acetylneuraminic acid residues on red blood cells (RBCs), leading to the exposure of the T cryptantigen and polyagglutinability of RBCs, a process known as T activation. Data suggest a pathogenic role of exposed T antigens on glomeruli interacting with naturally occurring anti-T in the development of renal dysfunction in pHUS. By reducing the levels of anti-T and neuraminidase, plasma exchange (PE) may have a role in the treatment of severe cases of pHUS. A previously healthy 2-year-old boy presented with acute renal failure, thrombocytopenia, microangiopathic hemolytic anemia, pneumococcal infection, and T activation of RBCs. A diagnosis of pHUS was made. Due to rapid clinical decline, daily single-volume PE with 5 percent albumin replacement was initiated. Infusion of additional plasma was avoided by using only saline-washed RBCs for transfusion. He made a full recovery after 13 PEs and remained well at follow-up 7 months later. Polyagglutinability of RBCs was shown by mixing patient RBCs with five normal donor sera. The agglutination assays with a panel of lectins confirmed the specificity of exposed T antigen as the cause of polyagglutinability. The dramatic response seen in this patient suggests that PE utilizing albumin replacement may benefit patients with severe pHUS.