Coombs Positive Thrombotic Thrombocytopenic Purpura in a Male Pediatric Patient: An Urgent Diagnostic Challenge.

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy often caused by deficiency of von Willebrand (vW) factor cleaving protease, ADAMTS-13, leading to large vW multimers and intravascular platelet aggregation. Hemolysis in TTP is mechanical and nonimmune mediated, thus Coombs testing is usually negative. We report a case of an adolescent with thrombocytopenia and Coombs positive anemia, diagnosed with Evans syndrome, but ultimately found to have TTP. TTP should be considered in children with thrombocytopenia and Coombs positive anemia who are refractory to steroids or develop signs of microangiopathy.  Recognition of this presentation can lead to life-saving treatment with plasma exchange.