Prevalence of factor XIII Val34Leu polymorphism in patients affected by spontaneous subconjunctival hemorrhage.

Purpose: To verify the prevalence of Val34Leu polymorphism in factor XIII A-chain gene (FXIII Val34Leu) in patients with spontaneous subconjunctival hemorrhage (SCH).
Design: Nonrandomized case-control study.
Methods: One hundred seven white patients suffering from one or more episodes of idiopathic SCH and 107 healthy subjects were matched for age and gender, and genotyped for FXIII Val34Leu. Anamnestic, ophthalmologic, cardiovascular, and serologic examinations were performed.
Results: Frequency of FXIII mutated allele (Leu34) was significantly higher in SCH patients than in controls. Computing together heterozygotes (Val/Leu) and homozygotes (Leu/Leu), genotype distribution was statistically different. In a conditional logistic regression model, the comparison of the three separated genotypes, performed among 25 patients with recurrent idiopathic SCHs and controls, gave significant differences for both Val/Leu and Leu/Leu variables.
Conclusion: Both homozygosity and heterozygosity for FXIII Val34Leu predispose to idiopathic SCH, emphasizing the role of Leu34 allele as inherited risk factor for spontaneous, especially recurrent, SCHs.