Plasminogen Deficiency: An Additional Risk Factor for Thrombosis in a Family with Factor V R506Q Mutation?

Combined heterozygous plasminogen deficiency and factor V Leiden defect in the same kindred

Combined plasminogen deficiency and resistance to activated protein C defect (factor V Leiden) have been described in a few families and associated with a variable occurrence of thrombotic events. Here we describe a new family with thrombophilia and the presence of hypoplasminogenemia and factor V Leiden mutation. In addition, a brief review of the literature is presented. Nine patients belonging to this kindred underwent coagulation study for hereditary thrombophilia, which included plasminogen antigen and activity assays, an activated protein C resistance test, and genetic analysis for factor V Leiden mutation and for prothrombin variant 20210A. The proposita, a 40-year-old asymptomatic female with a family history of thrombotic diathesis, was affected by heterozygous plasminogen deficiency. Hypoplasminogenemia was found also in her two sisters, in one instance associated with factor V Leiden mutation. The mother was the putative carrier of hypoplasminogenemia, but she refused to be studied. The symptomatic father was heterozygous for factor V Leiden mutation, but presented with normal plasminogen levels. Among the available siblings investigated from the paternal side, resistance to activated protein C due to factor V Leiden mutation was found in three patients, one of whom experienced venous thromboembolism. Another uncle with a history of thrombotic disease showed no coagulation abnormalities. These findings together with the data from literature confirm the role of factor V Leiden as an independent risk factor for venous thromboembolism, whereas isolated hypoplasminogenemia does not seem to increase the risk for thrombosis. There is no clear evidence that the coinheritance of these two defects may be associated with an additional risk for thrombosis compared with the presence of factor V Leiden mutation alone.

Familial association of hypoplasminogenemia and heterozygous factor V deficiency

The coinheritance of hypoplasminogenemia and heterozygous factor V deficiency in a relative with thrombotic disease and no hemorrhagic tendency is described. The proposita, a 28-year-old woman, suffered from neurologic disturbances due to two ischemic cerebral lesions confirmed by nuclear magnetic resonance scan. She was found to be affected with heterozygous plasminogen deficiency in a coagulation study for inherited thrombophilia. Moreover, she disclosed a prolongation of prothrombin time and activated partial thromboplastin time, which was compatible with heterozygous factor V deficiency. Her father, with a history of deep vein thrombosis, was also affected with plasminogen deficiency, as well as three brothers and one sister who were asymptomatic. The mother of the proposita showed borderline or slightly decreased factor V levels and normal plasminogen levels; she was therefore considered to be heterozygous for factor V deficiency. Heterozygous factor V deficiency was also found in one brother and one sister of the proposita, and they were both asymptomatic. Among the other available family members, one brother and one sister of the proposita, all asymptomatic for either thrombotic or bleeding events, showed a normal clotting and fibrinolytic profile. To our knowledge, this is the first case of combined heterozygous plasminogen and factor V deficiency in the same family. Two of six patients with hypoplasminogenemia showed thrombotic events, and in one of these symptomatic cases the coexistence of factor V deficiency did not prevent the occurrence of thrombosis. As expected, no hemorrhagic tendency was observed in patients with heterozygous factor V deficiency, who may be mildly symptomatic only in 10% of cases.

Laboratory evaluation of hypercoagulable states

The number of well-characterized hereditary and acquired hypercoagulable conditions is increasing, such that in many thrombophilic patients, the laboratory can now identify a hypercoagulable condition. This review describes the currently known hypercoagulable states that predispose patients to venous, and in some instances, arterial thrombosis. For each condition, the discussion includes the incidence, magnitude of the thrombotic risk in the general population in comparison with symptomatic families, synergistic interactions among the various hypercoagulable conditions, molecular pathogenesis, and interpretation of laboratory test results. In addition, recommendations for laboratory testing are summarized.

Plasminogen Kanagawa-I, a novel missense mutation, is caused by the amino acid substitution G732R

A new dysplasminogen, plasminogen Kanagawa-I, was identified in a healthy male with no previous thrombotic episodes. His plasma plasminogen (PLG) activity was 51.4% of that of normal pooled plasma (reference interval 70-130%) and the antigen level was 94.2% of that of normal pooled plasma (reference interval 80-150%). Nucleotide sequencing revealed a heterozygous G to A transition in exon 18, which resulted in an amino acid substitution of G732R. Both the proband's father and paternal grandfather were heterozygous for this mutation. Interestingly, the grandfather was found to be a compound heterozygote for plasminogen Kanagawa-I and Tochigi (A601T), so that his plasminogen activity and antigen level was 7.7% and 87.2% of that of normal pooled plasma, respectively. However, he has never been affected by significant thrombosis.

An unknown genetic defect increases venous thrombosis risk, through interaction with protein C deficiency

We used two-locus segregation analysis to test whether an unknown genetic defect interacts with protein C deficiency to increase susceptibility to venous thromboembolic disease in a single large pedigree. Sixty-seven pedigree members carry a His107Pro mutation in the protein C gene, which reduces protein C levels to a mean of 46% of normal. Twenty-one carriers of the mutation and five other pedigree members had verified thromboembolic disease. We inferred the presence in this pedigree of a thrombosis-susceptibility gene interacting with protein C deficiency, by rejecting the hypothesis that the cases of thromboembolic disease resulted from protein C deficiency alone and by not rejecting Mendelian transmission of the interacting gene. When coinherited with protein C deficiency, the interacting gene conferred a probability of a thrombotic episode of approximately 79% for men and approximately 99% for women, before age 60 years.

Low risk of venous thrombosis in two families with combined type I plasminogen deficiency and factor V R506Q mutation

Two families with type I plasminogen deficiency and APC resistance are reported. The proposita of family A suffered from ischemic stroke when taking estrogen-progesterone-containing oral contraceptive. Several hemostatic challenges in the past (ovariectomy, appendectomy, and two pregnancies) were without thrombosis. Plasminogen activity and antigen (60 and 58%, normal range 72-136 and 69-135%, respectively) were reduced, and an increased APC resistance (APC-SR= 1.55; normal range 1.8-3.00) associated with G --> A change at 1,691 nucleotide position in exon 10 of FV gene (FV Leiden) was observed. The asymptomatic son had isolated plasminogen deficiency (activity 57% and antigen 60%) whereas the asymptomatic daughter had isolated APC resistance (APC-SR = 1.61) and FV Leiden mutation. The proposita of family B, referred for superficial thrombophlebitis, had low plasminogen levels (activity 55% and antigen 53%) and APC resistance (APC-SR = 1.5) whereas the asymptomatic mother and the brother had isolated APC resistance (APC-SR = 1.62 and 1.8, respectively) and the asymptomatic father isolated plasminogen deficiency (activity 61% and antigen 62%). These data suggest that the combination of plasminogen deficiency and APC resistance probably does not significantly increase the risk of venous thrombosis. However, larger experience with additional cases is needed to definitely assess the magnitude of thrombotic risk in these families.

Hemorrhagic and thrombotic disorders due to factor V deficiencies and abnormalities: an updated classification

The recent description of a factor V abnormality (factor V Leiden) associated with an increased incidence of thrombosis has considerably increased interest in this clotting factor. The discovery of this new clinical entity indicated the need for an updated classification of factor V defects. These should be divided into hemorrhagic and thrombotic disorders. A proper classification of hemorrhagic disorders should include: 1) homozygous and heterozygous 'true' factor V deficiency; and 2) combined factor V and factor VIII deficiencies. The latter should be subdivided in Type I (association type) and Type II (common defect). A suitable classification of the thrombotic factor V defects should include: 1) homozygous and heterozygous factor V Leiden; and 2) combined heterozygous factor V Leiden and heterozygous 'true' factor V deficiency. The presence of thrombosis in these latter patients, often as severe as those seen in homozygous patients with activated protein C (APC) resistance, allows important considerations on the functions of factor V. It would seem that half the normal level of factor V activity and antigen is unable to protect against thrombosis in patients with heterozygous APC resistance. An accurate evaluation of factor V activity and antigen is indicated in all patients with suspected factor V defects. The first suspicion may be obtained by the presence of a mild prolongation of prothrombin time and of partial thromboplastin time. The suspicion should then be immediately confirmed by specific factor V activity and antigen assays. This approach is of great importance even for the presumptive diagnosis of pseudohomozygosis for APC resistance. In fact, in these cases, factor V activity is about 50% of normal, whereas factor V antigen is 100% of normal. In heterozygous 'true' factor V deficiency both activity and antigen are about 50% of normal.