Peculiar laboratory phenotype/ genotype relationship due to compound inherited protein C defects in a child with severe venous thromboembolism

Summary

A 7-years-old child who developed unprovoked deep vein thrombosis (DVT) and pulmonary embolism (PE) was tested for inherited thrombophilia. Protein C (PC) antigen level (87 %) and PC coagulometric and amidolytic activities (12 % and 11 %, respectively) were consistent with a homozygous PC type IIA phenotype.

The patient was carrier of two heterozygous missense mutations causing p.Arg32Cys substitution associated with a type I PC defect (“null allele”, from the paternal side) and p.Gly433Ser substitution responsible for a type IIA PC defect (from the maternal side). Thus, the apparently normal PC antigen level in the proband was misleading in the interpretation of phenotype/genotype relationship of this compound PC defect. The child was also carrier of heterozygous prothrombin G20210A variant.

Severe venous thromboembolism can occur in otherwise healthy children with complex inherited thrombophilia. Careful laboratory characterization of the phenotype/genotype relationship can be crucial to correctly classify PC defects and for their management with anticoagulants or replacement therapy.

Zusammenfassung

Ein 7-jähriges Kind wurde aufgrund einer unprovozierten tiefen Venenthrombose (TVT) und Lungenembolie (LE) auf hereditäre Thrombophilien getestet. Der Antigen-Spiegel an Protein C (PC) (87 %), sowie Aktivität von PC, welche mittels koagulometrischen und chromogenem (amidolytischem) Assay bestimmt wurde (12 % bzw. 11 %), waren mit einem homozygoten PC Typ IIA Phänotyp vereinbar.

Tatsächlich war der Patient compound heterozygot, d. h. Träger von zwei unterschiedlichen Missense-Mutationen des PC-Gens: eine p.Arg32Cys Substitution, dass mit einer type I PC Defekt (“null Allel”, von der väterlichen Seite) assoziiert ist, und eine p.Gly433Ser Substitution, dass für einer type II PC defekt (von der mütterlichen Seite) verantwortlich ist.

Dies führte zu einem irreführend normalen PC Antigen Spiegel bei dem Probanden im Rahmen der Interpretation der Phänotyp/Genotyp- Beziehung dieses kombinierten PC Defekts. Das Kind war zudem heterozygoter Träger der Prothrombin G20210A Mutation.

Schwere venöse Thromboembolien können bei ansonsten gesunden Kindern mit komplex vererbten Thrombophilien auftreten. Eine sorgfältige Laborcharakterisierung der Phänotyp-/ Genotyp-Beziehung kann entscheidend sein für die korrekte Klassifizierung von PC-Defekten sowie für das Management mit Antikoagulantien oder Ersatztherapie.

Keywords

Protein C defects - children - thrombosis - thrombophilia - phenotype/genotype relationship

Schlüsselwörter

Protein C defekten - Kinder - Thrombosis - Thrombophilie - Phänotyp-/Genotyp-Beziehung

 

• References

• 1 Tait RC, Walker ID, Reitsma PH. et al. Prevalence of protein C deficiency in the healthy population. Thromb Haemost 1995; 73: 87-93.
• 2 Tirado I, Mateo J, Soria JM. et al. Contribution of prothrombin 20210A allele and factor V Leiden mutation to thrombosis risk in thrombophilic families with other hemostatic deficiencies. Haematologica 2001; 86: 1200-1208.
• 3 Yang LH, Zheng FX, Chen Y. et al. The significance of F139V mutation on thrombotic events in compound heterozygous and homozygous protein C deficiency. Blood Coagul Fibrinolysis 2014; 25: 824-830.
• 4 Goldenberg NA, Manco-Johnson MJ. Protein C deficiency. Haemophilia 2008; 14: 1214-1221.
• 5 Girolami A, Simioni P, Lazzaro AR, Girolami B, Prandoni P. A family with an abnormal protein C and a thrombotic tendency. Haematologia (Budap) 1993; 25: 25-33.
• 6 Girolami A, Simioni P, Girolami B. et al. A novel dysfunctional protein C (protein C Padua 2) associated with a thrombotic tendency: substitution of Cys for Arg-1 results in a strongly reduced affinity for binding of Ca++. Br J Haematol 1993; 85: 521-527.
• 7 Wojcik EG, Simioni P, dBerg M, Girolami A, Bertina RM. Mutations which introduce free cysteine residues in the Gla-domain of vitamin K dependent proteins result in the formation of complexes with alpha 1-microglobulin. Thromb Haemost 1996; 75: 70-75.
• 8 Simioni P, Kalafatis M, Tormene D. et al. Abnormal propeptide processing resulting in the presence of two abnormal species of protein C in plasma: characterization of the dysfunctional protein C Padua3 (protein C(R-1L/propeptide)). Thromb Haemost 2001; 86: 1017-1022.
• 9 Simioni P, Kalafatis M, Millar DS. et al. Compound heterozygous protein C deficiency resulting in the presence of only the beta-form of protein C in plasma. Blood 1996; 88: 2101-2108.
• 10 Bulato C, Radu CM, Campello E. et al. New prothrombin mutation (Arg596Trp, prothrombin Padua 2) associated with venous thromboembolism. Arterioscler Thromb Vasc Biol 2016; 36: 1022-1029.
• 11 Foster DC, Yoshitake S, Davie EW. The nucleotide sequence of the gene for human protein C. Proc Natl Acad Sci U S A 1985; 82: 4673-4677.
• 12 Simioni P, Sanson BJ, Prandoni P. et al. Incidence of venous thromboembolism in families with inherited thrombophilia. Thromb Haemost 1999; 81: 198-202.
• 13 Seligsohn U, Berger A, Abend M. et al. Homozygous protein C deficiency manifested by massive venous thrombosis in the newborn. N Engl J Med 1984; 310: 559-562.
• 14 Marciniak E, Wilson HD, Marlar RA. Neonatal purpura fulminans: a genetic disorder related to the absence of protein C in blood. Blood 1985; 65: 15-20.
• 15 Cafolla A, D’Andrea G, Baldacci E, Margaglione M, Mazzucconi MG, Foa R. Hereditary protein C deficiency and thrombosis risk: genotype and phenotype relation in a large Italian family. Eur J Haematol 2012; 88: 336-339.
• 16 Reitsma PH, Bernardi F, Doig RG. et al. Protein C deficiency: a database of mutations, 1995 update. On behalf of the Subcommittee on Plasma Coagulation Inhibitors of the Scientific and Standardization Committee of the ISTH. Thromb Haemost 1995; 73: 876-889.
• 17 Ireland HA, Boisclair MD, Taylor J. et al. Two novel (R(-11)C; T394D) and two repeat missense mutations in the protein C gene associated with venous thrombosis in six kindreds. Hum Mutat 1996; 07: 176-179.
• 18 Spek CA, Koster T, Rosendaal FR, Bertina RM, Reitsma PH. Genotypic variation in the promoter region of the protein C gene is associated with plasma protein C levels and thrombotic risk. Arterioscler Thromb Vasc Biol 1995; 15: 214-218.
• 19 Aiach M, Nicaud V, Alhenc-Gelas M. et al. Complex association of protein C gene promoter polymorphism with circulating protein C levels and thrombotic risk. Arterioscler Thromb Vasc Biol 1999; 19: 1573-1576.
• 20 Tang W, Basu S, Kong X. et al. Genome-wide association study identifies novel loci for plasma levels of protein C: the ARIC study. Blood 2010; 116: 5032-5036.
• 21 Pintao MC, Roshani S, de Visser MC. et al. High levels of protein C are determined by PROCR haplotype 3. J Thromb Haemost 2011; 09: 969-976.
• 22 Campello E, Spiezia L, Radu CM. et al. Circulating microparticles and the risk of thrombosis in inherited deficiencies of antithrombin, protein C and protein S. Thromb Haemost 2016; 115: 81-88.
• 23 Regnault V, Boehlen F, Ozsahin H. et al. Anti-protein S antibodies following a varicella infection: detection, characterization and influence on thrombin generation. J Thromb Haemost 2005; 03: 1243-1249.
• 24 Tormene D, Gavasso S, Rossetto V, Simioni P. Thrombosis and thrombophilia in children: a systematic review. Semin Thromb Hemost 2006; 32: 724-728.
• 25 Young G, Albisetti M, Bonduel M. et al. Impact of inherited thrombophilia on venous thromboembolism in children: a systematic review and metaanalysis of observational studies. Circulation 2008; 118: 1373-1382.
• 26 Tormene D, Simioni P, Prandoni P. et al. The incidence of venous thromboembolism in thrombophilic children: a prospective cohort study. Blood 2002; 100: 2403-2405.