PF4-associated immune thrombocytopenia and thrombosis (PITT)-More than heparin and vaccines.

A young woman presented with portal vein thrombosis and thrombocytopenia and developed further extensive thrombosis following treatment with heparin. Despite no previous heparin exposure, she was found to be strongly positive for anti-platelet factor 4 (PF4) antibodies. She had acute cytomegalovirus (CMV) infection and a monoclonal gammopathy. Commentary on: Nicolson et al. Anti-PF4 mediated thrombocytopenia and thrombosis associated with acute cytomegalovirus infection displays both HIT-like and VITT-like characteristics. Br J Haematol 2025; 206:1737-1742.