Severe thrombotic tendency associated with a type I plasminogen deficiency

A protein C and plasminogen compound heterozygous mutation and a compound heterozygote of protein C in two related Chinese families

Hereditary protein C (PC) deficiency and congenital plasminogen (PLG) deficiency are both factors of thrombophilia which were caused by PC and PLG gene mutations with the characteristics of activity and antigen decreasing inconsonantly. To illustrate the connection between gene mutations and the corresponding deficiencies of PC and PLG, we studied two related cases. The proband 1 showed a cranial venous sinus thrombosis with reduced activities of PC and PLG, 55 and 56%, respectively. And the proband 2 was his asymptomatic nephew who had a reduced PC activity of 27%. All the PC genes (PROC) and PLG genes were amplified by PCR with direct sequencing. Then these detected mutations were analyzed by conservation, bioinformatics, and model. Genetic analysis detected two compound heterozygous missense mutations: the proband 1 carried a p.Gly86Asp in PC and a p.Ala601Thr in PLG, whereas the proband 2 took two mutations of PC (p.Gly86Asp and p.Arg147Trp). All conservation, bioinformatics prediction, and model analysis results indicated that these mutations probably affected the structures and stabilities of the matching proteins. We speculated that the three mutations are responsible for the reduction of PC activity and PLG activity. Furthermore, the p.Gly86Asp of PC has been detected for the first time in the world.

The Unravelling of the Genetic Architecture of Plasminogen Deficiency and its Relation to Thrombotic Disease

Although plasminogen is a key protein in fibrinolysis and several mutations in the plasminogen gene (PLG) have been identified that result in plasminogen deficiency, there are conflicting reports to associate it with the risk of thrombosis. Our aim was to unravel the genetic architecture of PLG in families with plasminogen deficiency and its relationship with spontaneous thrombotic events in these families. A total of 13 individuals from 4 families were recruited. Their genetic risk profile of thromboembolism was characterized using the Thrombo inCode kit. Only one family presented genetic risk of thromboembolism (homozygous carrier of F12 rs1801020 and F13A1 rs5985). The whole PLG was tested using Next Generation Sequencing (NGS) and 5 putative pathogenic mutations were found (after in silico predictions) and associated with plasminogen deficiency. Although we can not find genetic risk factors of thrombosis in 3 of 4 families, even the mutations associated with plasminogen deficiency do not cosegregated with thrombosis, we can not exclude plasminogen deficiency as a susceptibility risk factor for thrombosis, since thrombosis is a multifactorial and complex disease where unknown genetic risk factors, in addition to plasminogen deficiency, within these families may explain the thrombotic tendency.

Plasminogen deficiency

Plasminogen (plg) deficiency has been classified as (i) hypoplasminogenemia or 'true' type I plg deficiency, and (ii) dysplasminogenemia, also called type II plg deficiency. Both forms, severe hypoplasminogenemia and dysplasminogenemia, are not causally linked to venous thrombosis. Dysplasminogenemia does not lead to a specific clinical manifestation and probably represents only a polymorphic variation in the general population, mainly in Asian countries. Severe hypoplasminogenemia is associated with compromised extracellular fibrin clearance during wound healing, leading to pseudomembraneous (ligneous) lesions on affected mucous membranes (eye, middle ear, mouth, pharynx, duodenum, upper and lower respiratory tract and female genital tract). Ligneous conjunctivitis is by far the most common clinical manifestation. More than 12% of patients with severe hypoplasminogenemia exhibit congenital occlusive hydrocephalus. In milder cases of ligneous conjunctivitis, topical application of plg-containing eye drops, fresh frozen plasma, heparin, corticosteroids or certain immunosuppressive agents (such as azathioprine) may be more or less effective. Oral treatment with sex hormones was successful in two female patients with ligneous conjunctivitis. In severe cases with possibly life-threatening multi-organ involvement, true therapeutic options are not available at present. The plg-knockout mouse is a useful tool to study the many different properties of plg in a variety of settings, such as wound healing, tissue repair and tissue remodeling, virulence and invasiveness of certain bacteria in the human host, tumor growth and dissemination, as well as arteriosclerosis.

A K19E missense mutation in the plasminogen gene is a common cause of familial hypoplasminogenaemia

The prevalence of familial plasminogen deficiency in Scotland has recently been calculated at 2.9/1000. However, little is known of the molecular genetic background and the frequency of plasminogen gene mutations in most cases of inherited plasminogen deficiency. Having previously identified 28 unrelated subjects with familial plasminogen deficiency from a cohort of 9611 blood donors, we have now reviewed 19 of these 28 subjects and screened the plasminogen gene in 15 subjects with hypoplasminogenaemia (plus five relatives) and four subjects with dysplasminogenaemia for mutations and polymorphisms. A missense mutation K19E in the plasminogen gene was found in 13 of the 15 propositi with hypoplasminogenaemia, in one of these in a homozygous manner. In two subjects with hypoplasminogenaemia, two new mutations (P353A and R471X) were identified. These three different mutations, if inherited in a homozygous or compound-heterozygous manner, may be associated with the development of ligneous conjunctivitis. In four subjects with dysplasminogenaemia, three heterozygous mutations (C548G, n = 1; A601T, n = 1; G693R, n = 2) were found. None of the propositi with plasminogen deficiency developed venous thrombosis at any time. In conclusion, the K19E mutation in the plasminogen gene is a common cause of hypoplasminogenaemia in Scotland, with an estimated prevalence of around 0.14%.

Plasminogen and tissue-type plasminogen activator deficiency as risk factors for thromboembolic disease

OBJECTIVE

To review the published evidence for an association between a deficiency of plasminogen or tissue-type plasminogen activator (tPA) and the risk of thrombosis.

DATA SOURCES

Review of the medical literature, with an emphasis on the last 10 years.

DATA EXTRACTION AND SYNTHESIS

After an initial assessment of the literature, including review of clinical study design and laboratory methods, a draft manuscript summarizing the findings was prepared and circulated to participants in the College of American Pathologists Conference on Diagnostic Issues in Thrombophilia. The key findings and each recommendation were presented for discussion at the conference. Recommendations were accepted if a consensus of the 27 experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.

CONCLUSIONS

The consensus of the conference was that routine laboratory assessment of plasminogen and tPA concentration in patients with thrombophilia is not warranted at this time. Analysis of plasminogen and tPA gene alterations in patients with thrombophilia is also not warranted at this time. Determination of plasminogen concentration should be performed in patients suspected of having ligneous conjunctivitis.

Combined Ala601-Thr-type dysplasminogenaemia and antiphospholipid antibody syndrome in a patient with recurrent thrombosis

A 44-year-old man was admitted to our hospital because of recurrent thrombosis. Laboratory findings showed that he had antiphospholipid antibody syndrome (APS) associated with systemic lupus erythematosus. Plasminogen activity was reduced (21%), but its antigenic level was rather elevated (16.4 mg/dl). The discrepancy of plasminogen activity and antigen levels was also found in his three daughters. Gene analysis revealed a homozygous missense mutation (Ala601-->Thr) at exon 15 of the plasminogen gene in the patient and a heterozygous mutation in his three daughters, suggesting that the patient has dysplasminogenaemia, which was reported as "plasminogen Tochigi." Although it still remains controversial whether both dysplasminogenaemia and plasminogen deficiency are relevant independent thrombotic risk factors, the combination of this deficiency and APS should be considered as a strong predisposition to thrombosis in this patient.

Effect of individual plasma lipoprotein(a) variations in vivo on its competition with plasminogen for fibrin and cell binding: An in vitro study using plasma from children with idiopathic nephrotic syndrome

Simultaneous natural changes in lipoprotein(a) [Lp(a)] and plasminogen occur in the nephrotic syndrome and offer a unique opportunity to investigate their effects on plasminogen activation under conditions fashioned in vivo. Plasminogen, Lp(a), and apolipoprotein(a) in plasma were characterized, and their competitive binding to carboxy-terminal lysine residues of fibrin and cell membrane proteins was determined in nephrotic children during a flare-up of the disease (61 cases) and after 6 weeks (33 cases) and 6 months (42 cases) of remission. Low plasminogen concentrations (median 1.34 micromol/L, range 0.39 to 1.96 micromol/L) and high Lp(a) levels (median 0.27 g/L, range 0.07 to 2. 57 g/L) were detected at flare-up. These changes were associated with an increased Lp(a) binding ratio onto fibrin (3.13+/-0.48) and cells (1.53+/-0.24) compared with binding ratios of control children (1.31+/-0.19 and 1.05+/-0.07, respectively) with normal plasminogen and low Lp(a) (median 0.071 g/L). After 6 weeks and 6 months of remission, the values for net decrease in Lp(a) binding to fibrin were 1.7+/-0.22 (after 6 weeks) and 1.88+/-0.38 (after 6 months) and were correlated with low Lp(a) concentrations (median 0.2 g/L, range 0.07 to 0.8 g/L; and median 0.12 g/L, range 0.07 to 1.34 g/L) and inversely associated with increased plasminogen levels (median 1.82 micromol/L, range 1.4 to 2.1 micromol/L; and median 1.58 micromol/L, range 1.1 to 2.1 micromol/L). These studies provide the first quantitative evidence that binding of Lp(a) to lysine residues of fibrin and cell surfaces is directly related to circulating levels of both plasminogen and Lp(a) and that these glycoproteins may interact as competitive ligands for these biological surfaces in vivo. This mechanism may be of relevance to the atherothrombotic role of Lp(a), particularly in nephrotic patients.

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.

Phlegmasia caerulea dolens and venous gangrene

Phlegmasia caerulea dolens and venous gangrene are rare conditions that tend to occur in association with malignancy. They are characterized by total or near-total occlusion of the venous drainage of the limb, including the microvascular collaterals. Associated mortality and morbidity rates are high, especially when progression to venous gangrene has occurred. Treatment options are limited; elevation and anticoagulation are recommended as first-line management. Experience with thrombolysis has been disappointing although intra-arterial administration of thrombolytic agents may improve results. Thrombectomy cannot be advocated routinely. Little advance in management, or in life and limb salvage, has been made in the past 30 years.

Unusual thrombotic-like retinopathy (Coats' disease) associated with congenital plasminogen deficiency type I

A new kindred with heterozygous plasminogen deficiency type I is described. The proband, a 17-year-old male, showed a peculiar thrombotic-like retinal picture compatible with Coats' disease. Extensive coagulation studies revealed decreased levels of both plasminogen activity and antigen to about 50% of normal values. Five out of 13 family members from the paternal side showed the same fibrinolytic defect. In two cases, a history of recurrent phlebites of the lower limbs was present. One unaffected patient also had a superficial phlebites at a young age; her plasminogen levels were shown to be within normal limits, but a long-standing oestroprogestinic intake could have influenced and normalized the results. No other family member showed retinal abnormality. This is the first case of hypoplasminogenaemia associated with Coats' disease. A possible role of the fibrinolytic defect in the pathogenesis of this unusual retinopathy is suggested. Finally, the occurrence of thrombotic manifestations in other affected family members supports the opinion that plasminogen deficiency should be considered as a potential risk factor for thrombosis.

Cerebral venous thrombosis with plasminogen deficiency

We describe a patient with inherited plasminogen deficiency who developed extensive cerebral venous thrombosis. Several other conditions that might have contributed to a hypercoagulable state, including mild thrombocytosis, thyrotoxicosis, and a chronic inflammatory lung disorder, were present. We also discuss the evidence linking plasminogen deficiency with a thrombophilic state. The diagnosis of cerebral venous thrombosis in this case was readily established by nuclear magnetic resonance imaging, a technique that is ideally suited for the evaluation and follow-up of patients with this condition.