Heterozygous type I plasminogen deficiency is associated with an increased risk for thrombosis: a statistical analysis in 20 kindreds.

The prevalence of thrombosis in patients with heterozygous type I plasminogen deficiency was studied. Fifteen kindreds described in the literature and a further five additional kindreds from the authors' Department were gathered. The prevalence of thrombotic events in all the patients with plasminogen deficiency was 23.6% (22 out of 93 patients), which decreased to 9.5% (seven of 74 patients) when the propositi were excluded. The 95 unaffected siblings were asymptomatic. The comparison between the prevalence of thrombosis in patients with plasminogen deficiency, with or without inclusion of the index patients, and in unaffected family members was statistically significant in both instances (P < 0.0001 and P = 0.002, respectively). Analogous results were obtained from construction of thrombosis-free survival curves, which showed that in plasminogen deficient patients, either with or without inclusion of the propositi, the probability of developing thrombotic manifestations is significantly higher than in unaffected siblings (P = 0.002 and P = 0.043, respectively). It is concluded that congenital heterozygous plasminogen deficiency should be considered a risk factor for thrombosis, even though the probability of having a thrombotic event seems to be lower than in other thrombophilic conditions, such as hereditary defects of clotting factor inhibitors.