PF4 and deep vein thrombosis: Despite no recent history of vaccination or heparin treatment, the aggressive thrombosis and thrombocytopenia triggered consideration of PF4‐associated immune thrombocytopenia and thrombosis; Chemiluminescence testing for anti‐PF4 antibodies was negative, but ELISA testing was strongly positive (>3.0 OD) with 98% neutralization with 0.5 U/mL heparin.