Catastrophic thrombotic syndromes are characterized by rapid onset of multiple thromboembolic occlusions affecting diverse vascular beds. Patients may have
multiple events on presentation, or develop them rapidly over days to weeks.
Several disorders can present with this extreme clinical phenotype, including
catastrophic antiphospholipid syndrome (APS), atypical presentations of thrombotic
thrombocytopenic purpura (TTP) or heparin-induced thrombocytopenia (HIT), and Trousseau syndrome, but some  patients present with multiple thrombotic events in the absence of associated prothrombotic disorders. Diagnostic workup must rapidly determine which, if any, of these syndromes are present because therapeutic management is driven by the underlying disorder. With the exception of atypical presentations of TTP, which are treated with plasma exchange, anticoagulation
is the most important therapeutic intervention in these patients. Effective anticoagulation may require laboratory confirmation with anti–factor Xa levels in patients treated with heparin, especially if the baseline (pretreatment) activated partial thromboplastin time is prolonged.
Patients with catastrophic APS also benefit from immunosuppressive therapy and/or
plasma exchange, whereas patients with HIT need an alternative anticoagulant to
replace heparin. Progressive thrombotic events despite therapeutic anticoagulation
may necessitate an alternative therapeutic strategy. If the thrombotic process can be
controlled, these patients can recover, but indefinite anticoagulant therapy may be
appropriate to prevent recurrent events.
(Blood. 2015;126(11):1285-1293)