Case report of a fatal probable catastrophic antiphospholipid syndrome.

Catastrophic antiphospholipid syndrome (CAPS) is an uncommon but often fatal manifestation of antiphospholipid syndrome, marked by rapid, diffuse microvascular thrombosis with multiorgan involvement. In practice, the initial clinical picture can be indistinguishable from severe infection or sepsis-associated organ failure, which makes early diagnosis challenging. Early recognition is critical, as delayed intervention is associated with high mortality. We report a case of probable CAPS that presented with splenic infarction and shock in the setting of suspected sepsis. Her condition progressed quickly to multiorgan dysfunction, and antiphospholipid antibody testing repeatedly showed high-titer triple positivity. After probable CAPS was considered, triple therapy (high-dose glucocorticoids, anticoagulation, and therapeutic plasma exchange) was initiated, and she was discharged after clinical stabilization. She was later readmitted with fulminant infection and recurrent CAPS-like manifestations. Anticoagulation and plasma exchange were not restarted, and she died within 72 h, highlighting two contrasting courses under diagnostic uncertainty.