Diagnosis of exclusion
Must differentiate acute<unk>  from chronic<unk> , which suggests an underlying disorder
CBC shows normal cell lines except for the platelets (may have mild anemia)
Immune thrombocytopenic purpura
Marrow infiltration 
Thrombotic thrombocytopenic purpura
Viral infections 
Disseminated intravascular coagulation
Marrow suppression 
Heparin-Induced Thrombocytopenia 
Congenital thrombocytopenia