Homozygous protein C deficiency with purpura fulminans: report of a new case and a description of a novel mutation

A delayed presentation of homozygous protein C deficiency in a series of children: a report on two molecular defects

Pediatric emergency visits with purpura fulminans should raise the suspicion of hereditary homozygous protein C deficiency even beyond the neonatal age. The absence of this classical finding does not role the diagnosis out as atypical presentation with isolated intraocular bleeding was observed. Premarital counseling should be offered when family history suggests.

Two novel compound heterozygous mutations associated with types I and II protein C deficiency with unusual phenotypes

INTRODUCTION

We diagnosed two Chinese hereditary PC deficiency families and identified two novel compound heterozygous mutations (p.Arg194Cys/Gly324Ser and p.Glu274X/Asp297His) in the protein C (PROC) gene. The probands were classified as types I and II PC deficiency. The aim of this article is to access the influence of the mutations on PC activity, antigen and protein structure, and to evaluate whether there is abnormal PC localization.

MATERIALS AND METHODS

Genomic DNA of all family members was extracted, PCR amplified, and sequenced. The mutant PC expression plasmids were constructed. Expression assays, intracellular localization, and molecular modeling were performed.

RESULTS

Proband 1, a type II PC defect, harbored a compound heterozygous mutation, p.Arg194Cys/Gly324Ser in the PROC gene, underwent two thromboembolic events. Expression assays indicated that the p.Arg194Cys mutant lead to decreased PC activity and normal PC Ag levels. Intracellular localization showed that both p.Arg194Cys and p.Gly324Ser co-localized with the endoplasmic reticuli and the Golgi apparatus. Molecular modeling suggested that the p.Gly324Ser mutation disturbed the interaction between the heavy and light chains of the PC protein. Proband 2, a type I PC defect, harbored a compound heterozygous PROC gene mutation, p.Glu274X/Asp297His, presented with recurrent spontaneous abortion and right popliteal vein thrombosis. Expression results were in accordance with the PC changes of the patient, and existed in defective PC transport. Structural model suggested p.Glu274X lead to disulfide bond between heavy and light chain cannot form.

CONCLUSIONS

Our results confirm that two novel compound heterozygous PROC gene mutations are causative on the two PC deficiency families.

Molecular characterization of novel splice site mutation causing protein C deficiency

Congenital protein C deficiency is an inherited coagulation disorder associated with an elevated risk of venous thromboembolism. A Saudi Arabian male from a consanguineous family was admitted to neonatal intensive care unit in his first days of life because of transient tachypnea and hematuria. Laboratory investigations determined low platelet and protein C deficiency. Direct sequencing of PROC gene and RNA analysis were performed. Analysis of factor V Leiden (G1691A) and factor II (G20210A) mutations was also done. Novel homozygous splice site mutation c.796+3A>T was detected in the index case and segregation was confirmed in the family. RNA analysis revealed the pathogenicity of the mutation by skipping exon 8 of PROC gene and changing the donor splice site of the exon. Detection of the molecular cause of protein C deficiency reduces life threatening and facilitates inductive carrier testing, prenatal and preimplantation genetic diagnosis for families.

Use of human protein C concentrates in the treatment of patients with severe congenital protein C deficiency

Protein C is one of the major inhibitors of the coagulation system that downregulate thrombin generation. Severe congenital protein C deficiency leads to a hypercoagulability state that usually presents at birth with purpura fulminans and/or severe venous and arterial thrombosis. Recurrent thrombotic events are commonly seen. From the 1990’s, several virus-inactivated human protein C concentrates have been developed. These concentrates currently constitute the therapy of choice for the treatment and prevention of clinical manifestations of severe congenital protein C deficiency. This review summarizes the available information on the use of human protein C concentrates in patients with severe congenital protein C deficiency.

Hereditary protein C deficiency caused by the Ala267Thr mutation in the protein C gene is associated with symptomatic and asymptomatic venous thrombosis

INTRODUCTION

Protein C (PC) is a key anticoagulant that regulates hemostasis, and inherited deficiency of PC is an established risk factor for venous thrombosis (VT). The factor V Leiden mutation causing activated PC (APC) resistance is an additional risk factor for VT. Reduced PC levels in the circulation and/or APC resistance do not necessarily lead to thrombotic disease. In the present study we describe and characterize an ethnic Lebanese family in which individuals with reduced PC levels and APC resistance have various clinical symptoms.

METHODS

PC activity and antigen levels and APC resistance in the family members were quantified with commercial kits. Sequencing of PC DNA and mRNA was performed with BigDye Terminator Cycle Sequencing kit on the ABI 3730 Genetic Analyzer.

RESULTS

PC antigen and anticoagulant activity in the plasma of the proband and family members ranged from 9% to 69% and 3% to 63%, respectively, compared to levels measured in pooled normal plasma. Sequencing analysis of the PC gene of family members revealed that they were either homozygous or heterozygous for the Ala267Thr mutation. In addition, three of them exhibited APC resistance. None of the family members, except the proband, have had a history of VT despite that two of them have two genetic risk factors for thrombosis.

A neonate with homozygous protein C deficiency with a homozygous Arg178Trp mutation

Homozygous protein C deficiency affects approximately 1/400,000 to 1/1,000,000 live births. Homozygous protein C deficiency is associated with catastrophic and fatal purpura fulminans-like or thrombotic complications and disseminated intravascular coagulation. In the present patient, genetic study revealed Arg178Trp, a mutation found widely in European population; but this is the first case of homozygous Arg178Trp mutation who suffered from catastrophic purpura fulminans phenotype.