View source for Vaccine-induced immune thrombotic thrombocytopenia

==Background==

*Very rare

==Clinical Presentation==

*Follows recent vaccination within 4 to 30 days
*Can present with severe headache, visual changes, abdominal pain, nause and vomiting, back pain, dyspnea, leg pain or swelling, petechiae and easy bruising

==Investigations==

*CBC with platelet count and peripheral smear
*Imaging tor thrombosis based on the patient's signs and symptoms
*PF4-ELISA [[Heparin-induced thrombocytopenia|HIT]] assay, drawn before starting treatment, which is almost always positive with optical density greater than 2
*Fibrinogen, which is often low
*D-dimer, which is usually markedly elevated

==Diagnosis==

*All four criteria must be met:
**Recent COVID vaccine within 4 to 30 days previously
***So far only Johnson & Johnson and AstraZeneca
**Thrombosis, often cerebral or abdominal
**Thrombocytopenia, though they may be normal early in the course of illness
**Positive PF4 HIT ELISA

==Management==

*Should be started if there are signs or symptoms of serious thrombosis and positive imaging or low platelets
*Treated similarly to [[heparin-induced thrombocytopenia]]
**IVIg 1 g/kg daily for 2 days
**Non-heparin anticoagulation, such as [[argatroban]], [[bivalrudin]], DOACs, [[fondaparinux]], or [[danaparoid]]
**Thrombocytopenia or low fibrinogen are not absolute contraindications to anticoagulation, especially if platelets are >20 or rising
**Avoid platelet transfusions, unless serious or life-threatening bleeding

[[Category:Infectious diseases]]
[[Category:Hematology]]