A case of suspected streptococcus pneumoniae hemolytic uremic syndrome (pHUS) with utilization of minor crossmatching for platelet blood products lead to a diagnosis of atypical hemolytic uremic syndrome (aHUS)

Background.The action of bacterial neuraminidase of Streptococcus pneumoniae (SPN) results in exposure of the normally "hidden" Thomsen-Freidenreich antigen (T-antigen) found on erythrocytes and other tissues.This may lead to SPN-induced hemolytic uremic syndrome (pHUS) with subsequent hemolysis and end organ damage. pHUS can be identified by minor crossmatch incompatibility. We present a case of suspected pHUS that resulted in a compatible minor crossmatch which led to concern and eventually diagnosis of atypical HUS (aHUS). Design. A 6-month-old boy presented with respiratory failure. He was found to have blood cultures positive for SPN. Shiga toxin was negative and he had normal levels of ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13).The clinical team was concerned for pHUS and requested washed platelet product prior to a surgical procedure. Alternatively, a minor crossmatching was performed to determine the presence of T activation. An aHUS genetic panel was performed to sequence and analyze 12 genes encoding complement factors. Results. Minor crossmatch was performed using the patient's erythrocytes and plasma of ABO-identical platelets to be transfused. No agglutination was seen at immediate spin, 37°C, or anti-human globulin phase with valid controls. Genetics testing for complement mutations was consistent with aHUS. Conclusions. We present a case that is clinically consistent with pHUS. Confirmation of this entity is done with lectins or anti-sera that are not readily available. An alternative means of identifying pHUS is by demonstrating minor crossmatch incompatibility. By doing so, we excluded the possibility of pHUS and helped to elucidate a definitive diagnosis of aHUS. Our goal is to share our experience of a practical approach in a time-sensitive situation that other clinical pathologists could utilize in suspected cases of T activation with a clinical picture of thrombotic microangiopathy.