Table 1.

Summary of clinical characteristics of patients with VITT

Patient 1Patient 2Patient 3Patient 4Patient 5Patient 6Patient 7
Age, y 48 32 21 46 43 44 42 
Sex Male Female Male Female Female Male Male 
Platelet count at presentation (×109/L); normal range, 150-450 16 98 113 7 11 35 21 
D-dimer at presentation (ng/mL); normal range, 0-250 62 342 6574 22 903 31 301 30 324 6807 27 000 
Fibrinogen at presentation (g/L); normal range, 1.5-4 1.2 <0.35 0.98 1.1 1.07 <0.35 2.36 
PT ratio at presentation; normal range, 0.8-1.2 1.2 1.5 1.3 1.2 1.1 1.4 1.1 
APTT ratio at presentation; normal range, 0.8-1.2 1 1.7 0.8 1.1 1.2 1.6 1.3 
HIT antibody screen at presentation (optical density); normal range, 0.01-0.4 2.45 2.17 2.8 >3.0 1.77 2.6 >3.0 
Heparin-induced platelet activation (HITAlert) at presentation    
 Platelet activation with serum, normal ≤8% 24.79% 31.2% 55% N/A (not done) N/A (not done) N/A (not done) 75.31% 
 Platelet activation with serum and heparin, normal ≤8% 18.53% 18% 36.5% N/A (not done) N/A (not done) N/A (not done) 22.63% 
 Platelet activation with serum and excess heparin, normal ≤8% 0.64% 3.68% 1.43% N/A (not done) N/A (not done) N/A (not done) 4.38% 
Clinical CVST CVST Ischemic stroke CVST CVST CVST CVST 
Days after vaccine at presentation 14 12 10 14 11 9 12 
Presentation symptoms Headaches, hematuria, petechial rash; subsequent development of left-side weakness Occipital headache Headache for 2-3 d; collapse; expressive dysphasia Headache Headache, aura, petechial rash Headache and vomiting for a few hours, followed by reduced conscious level Headache for 1 wk, development of right-side weakness; subsequent seizure and collapse 
Comorbidities Prostatitis None None Hypothyroidism; fibromyalgia; anxiety None None None 
Medications None None None Levothyroxine; sertraline; amitriptyline None None None 
Imaging findings at presentation CVST; subarachnoid hemorrhage CVST; subarachnoid hemorrhage; intraparenchymal hemorrhage Acute left ICA thrombus with multiple left middle cerebral artery territory infarctions CVST; intraparenchymal hemorrhage CVST CVST; left-side intracerebral hemorrhage; midline shift CVST; subarachnoid and intraparenchymal hemorrhage; globalized brain atrophy 
Immunosuppression regimen used IVIg 0.5 g/kg once daily for 2 consecutive days; dexamethasone 20 mg once daily for 3 d IVIg 1 g/kg for 2 consecutive days; dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg single dose; dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg single dose; dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg on 2 nonconsecutive days; dexamethasone 40 mg once daily for 3 d IVIg 1 g/kg on 2 nonconsecutive days dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg single dose; dexamethasone 40 mg (2 doses) 
Anticoagulant /antiplatelet regimen used Argatroban fondaparinux 7.5 mg SC; once daily (when platelets normalized) Argatroban Fondaparinux 7.5 mg once daily; apixaban 5 mg twice daily (on discharge) Fondaparinux 2.5 mg SC once daily (while platelets are <50 × 109/L); fondaparinux 7.5 mg SC once daily (when platelets ≥50 × 109/L) dabigatran 150 mg twice daily (on discharge) Fondaparinux 7.5 mg SC once daily Argatroban fondaparinux 7.5 mg SC once daily (when platelets ≥050 ×109/L) None 
Other treatments required Intubation Intubation, thrombectomy Thrombectomy None Plasma exchange Intubation, thrombectomy, decompressive craniotomy, plasma exchange, platelet transfusion Intubation, mannitol 
Timing of first serum sample After IVIg and dexamethasone After single dose of dexamethasone Before treatment Before treatment After IVIg and dexamethasone After IVIg and dexamethasone Before treatment 
Timing of second serum sample N/A Post -IVIg and dexamethasone Post-IVIg and dexamethasone Post-IVIg and dexamethasone Post-PEX Post-PEX N/A 
Days after IVIg that platelet count rose >50 × 109/L N/A; nadir 59 × 109/L (platelets 100 × 109/L 2 d after first IVIg infusion). 2 d N/A; nadir 52 × 109/L (platelets 198 × 109/L 3 d after IVIg infusion). 3 d 4 d 1 d N/A; died <24 h after IVIg. 
Outcome Clinically recovered at time of discharge from hospital after a 26-d admission. Death (support withdrawn after confirmation of brainstem death). Clinically recovered at time of discharge from hospital after a 10-d admission; ongoing mild right hand weakness and expressive dysphasia. Clinically recovered at time of discharge from hospital after a 16-d admission; 2 further admissions with headaches and drops in platelet counts; no further CVST; treated with (1st admission) prednisolone then (2nd admission) IVIg and rituximab; Remains in hospital. Clinically recovered at time of discharge from hospital after a 12-d admission. 36-d intensive care admission; ventilator-associated pneumonia; Limited neurological recovery; remains in hospital. Death 24 h after admission (rapid development of global ischemia before thrombectomy could be performed). 
Patient 1Patient 2Patient 3Patient 4Patient 5Patient 6Patient 7
Age, y 48 32 21 46 43 44 42 
Sex Male Female Male Female Female Male Male 
Platelet count at presentation (×109/L); normal range, 150-450 16 98 113 7 11 35 21 
D-dimer at presentation (ng/mL); normal range, 0-250 62 342 6574 22 903 31 301 30 324 6807 27 000 
Fibrinogen at presentation (g/L); normal range, 1.5-4 1.2 <0.35 0.98 1.1 1.07 <0.35 2.36 
PT ratio at presentation; normal range, 0.8-1.2 1.2 1.5 1.3 1.2 1.1 1.4 1.1 
APTT ratio at presentation; normal range, 0.8-1.2 1 1.7 0.8 1.1 1.2 1.6 1.3 
HIT antibody screen at presentation (optical density); normal range, 0.01-0.4 2.45 2.17 2.8 >3.0 1.77 2.6 >3.0 
Heparin-induced platelet activation (HITAlert) at presentation    
 Platelet activation with serum, normal ≤8% 24.79% 31.2% 55% N/A (not done) N/A (not done) N/A (not done) 75.31% 
 Platelet activation with serum and heparin, normal ≤8% 18.53% 18% 36.5% N/A (not done) N/A (not done) N/A (not done) 22.63% 
 Platelet activation with serum and excess heparin, normal ≤8% 0.64% 3.68% 1.43% N/A (not done) N/A (not done) N/A (not done) 4.38% 
Clinical CVST CVST Ischemic stroke CVST CVST CVST CVST 
Days after vaccine at presentation 14 12 10 14 11 9 12 
Presentation symptoms Headaches, hematuria, petechial rash; subsequent development of left-side weakness Occipital headache Headache for 2-3 d; collapse; expressive dysphasia Headache Headache, aura, petechial rash Headache and vomiting for a few hours, followed by reduced conscious level Headache for 1 wk, development of right-side weakness; subsequent seizure and collapse 
Comorbidities Prostatitis None None Hypothyroidism; fibromyalgia; anxiety None None None 
Medications None None None Levothyroxine; sertraline; amitriptyline None None None 
Imaging findings at presentation CVST; subarachnoid hemorrhage CVST; subarachnoid hemorrhage; intraparenchymal hemorrhage Acute left ICA thrombus with multiple left middle cerebral artery territory infarctions CVST; intraparenchymal hemorrhage CVST CVST; left-side intracerebral hemorrhage; midline shift CVST; subarachnoid and intraparenchymal hemorrhage; globalized brain atrophy 
Immunosuppression regimen used IVIg 0.5 g/kg once daily for 2 consecutive days; dexamethasone 20 mg once daily for 3 d IVIg 1 g/kg for 2 consecutive days; dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg single dose; dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg single dose; dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg on 2 nonconsecutive days; dexamethasone 40 mg once daily for 3 d IVIg 1 g/kg on 2 nonconsecutive days dexamethasone 40 mg once daily for 4 d IVIg 1 g/kg single dose; dexamethasone 40 mg (2 doses) 
Anticoagulant /antiplatelet regimen used Argatroban fondaparinux 7.5 mg SC; once daily (when platelets normalized) Argatroban Fondaparinux 7.5 mg once daily; apixaban 5 mg twice daily (on discharge) Fondaparinux 2.5 mg SC once daily (while platelets are <50 × 109/L); fondaparinux 7.5 mg SC once daily (when platelets ≥50 × 109/L) dabigatran 150 mg twice daily (on discharge) Fondaparinux 7.5 mg SC once daily Argatroban fondaparinux 7.5 mg SC once daily (when platelets ≥050 ×109/L) None 
Other treatments required Intubation Intubation, thrombectomy Thrombectomy None Plasma exchange Intubation, thrombectomy, decompressive craniotomy, plasma exchange, platelet transfusion Intubation, mannitol 
Timing of first serum sample After IVIg and dexamethasone After single dose of dexamethasone Before treatment Before treatment After IVIg and dexamethasone After IVIg and dexamethasone Before treatment 
Timing of second serum sample N/A Post -IVIg and dexamethasone Post-IVIg and dexamethasone Post-IVIg and dexamethasone Post-PEX Post-PEX N/A 
Days after IVIg that platelet count rose >50 × 109/L N/A; nadir 59 × 109/L (platelets 100 × 109/L 2 d after first IVIg infusion). 2 d N/A; nadir 52 × 109/L (platelets 198 × 109/L 3 d after IVIg infusion). 3 d 4 d 1 d N/A; died <24 h after IVIg. 
Outcome Clinically recovered at time of discharge from hospital after a 26-d admission. Death (support withdrawn after confirmation of brainstem death). Clinically recovered at time of discharge from hospital after a 10-d admission; ongoing mild right hand weakness and expressive dysphasia. Clinically recovered at time of discharge from hospital after a 16-d admission; 2 further admissions with headaches and drops in platelet counts; no further CVST; treated with (1st admission) prednisolone then (2nd admission) IVIg and rituximab; Remains in hospital. Clinically recovered at time of discharge from hospital after a 12-d admission. 36-d intensive care admission; ventilator-associated pneumonia; Limited neurological recovery; remains in hospital. Death 24 h after admission (rapid development of global ischemia before thrombectomy could be performed). 

APTT, activated partial thromboplastin time; ICA, internal carotid artery; IVIg, intravenous immunoglobulin; N/A, not available; PEX, plasma exchange; PT, prothrombin time; SC, subcutaneous.

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