Summary
Hereditary haemorrhagic telangiectasia (HHT) causes chronic nasal and gastrointestinal
haemorrhage. Prothrombotic agents are commonly used for severe haemorrhage. Thrombotic
risks have not been defined. In order to identify prothrombotic variables in HHT patients,
and assess their potential functional significance, a pilot ELISA-based study comparing
plasma proteins in healthy individuals with HHT to age/sex-matched non-HHT controls
was validated in a full study of 309 consecutive HHTaffected individuals. In the pilot
study, factor VIII (FVIII) and von Willebrand factor antigen concentrations were elevated
in the HHT group compared to non-HHT controls (p<0.0013, Mann- Whitney). Service laboratory
measurements confirmed high FVIII:Ag in 125 HHT-affected individuals with no recent
illhealth, intervention or venous thromboemboli. FVIII:Ag levels increased with age.
Logistic regression also suggested an age-independent association with HHT-associated
pulmonary arteriovenous malformations (AVMs). No association was demonstrated between
FVIII:Ag and acute phase response, disseminated intravascular coagulation, ABO group,
pulmonary artery pressure, or markers of HHT haemorrhage. Elevated FVIII:Ag were associated
with shortened activated partial thromboplastin times (APTTs), andVTE:VTE affected
20/309 (6.5%) HHT-affected individuals, at median age 61(36–71) years. Four VTE occurred
in factorV Leiden heterozygotes in the months following PAVM-associated brain abscess.
The strongest association with VTE was with log-transformed FVIII:Ag measured 10–132
months from VTE (odds ratio 2.41, 95% confidence intervals 1.254, 4.612, p=0.008).
Age made no additional contribution to VTE risk once adjusted for FVIII:Ag. In conclusion,
HHT-related elevation of FVIII:Ag levels may influence thrombotic risk in HHT. Individualised
risk-benefit considerations may be helpful in HHT management.
Keywords
Brain abscess - DIC - pulmonary AVMs - tranexamic acid - VWF