Much has been learned about thrombotic thrombocytopenic purpura (TTP) and 
heparin-induced thrombocytopenia (HIT) and much remains a diagnostic and 
management challenge. While the pentad of thrombocytopenia, microangiopathic 
hemolytic anemia, fever, and renal and neurologic abnormalities characterize the 
clinical presentation of TTP, few patients present with all signs and symptoms. 
Worse yet, the pentad and its components are seen in other so-called thrombotic 
microangiopathies that demand different treatment approaches. HIT is another 
systemic disorder presenting with thrombocytopenia and/or thrombosis with 
potential devastating consequences whose diagnosis is difficult and management 
is still evolving. Highlights of the conditions and clinical and laboratory 
hints that allow physicians to diagnose TTP and HIT efficiently and offer 
patients the best available therapeutic interventions are presented.