Thrombotic thrombocytopenic purpura.

A 6-year-old boy presented with microangiopathic hemolytic anemia, thrombo-cytopenia, altered sensorium and intractable bleeding. A diagnosis of thrombotic thrombocytopenic purpura was made and the child recovered dramatically after plasmapheresis. Recent developments in the understanding of TTP are reviewed, including the importance of a metaloprotease required to cleave multimers of von Willibrand factor.