Thrombotic thrombocytopenic purpura (TTP) is a rare microangiopathic disorder 
with high morbidity and significant mortality. The primary form of TTP is caused 
by severe deficiency, acquired or hereditary, of the von Willebrand factor 
cleaving protease (VWF-CP), ADAMTS-13. Because TTP occurs less frequently in 
children, general pediatricians are not well informed about the spectrum of 
clinical symptoms and altered laboratory values, increasing the risk of 
nondiagnosis and possible fatal outcome. If renal involvement is present, the 
condition can easily be misdiagnosed as hemolytic-uremic syndrome (HUS). We 
present a case series of children with severe VWF-CP deficiency with emphasis on 
the clinical heterogeneity responsible for misdiagnosis and inappropriate 
treatment. The inherited form may involve onset of symptoms ranging from 
isolated thrombocytopenia to the full clinical picture characteristic of 
classical TTP. The most common assumed diagnoses of oligosymptomatic forms are 
immune thrombocytopenia (ITP) and Evans syndrome, respectively. Accordingly, 
this article is directed towards pediatricians on neonatal and intensive care 
units, as well as their colleagues specializing in nephrology, hematology, and 
neurology.