Diagnosis and management of severe congenital protein C deficiency (SCPCD): Communication from the SSC of the ISTH

Thrombophilia Screening: Not So Straightforward

Although inherited thrombophilias are lifelong risk factors for a first thrombotic episode, progression to thrombosis is multifactorial and not all individuals with inherited thrombophilia develop thrombosis in their lifetimes. Consequently, indiscriminate screening in patients with idiopathic thrombosis is not recommended, since presence of a thrombophilia does not necessarily predict recurrence or influence management, and testing should be selective. It follows that a decision to undertake laboratory detection of thrombophilia should be aligned with a concerted effort to identify any significant abnormalities, because it will inform patient management. Deficiencies of antithrombin and protein C are rare and usually determined using phenotypic assays assessing biological activities, whereas protein S deficiency (also rare) is commonly detected with antigenic assays for the free form of protein S since available activity assays are considered to lack specificity. In each case, no single phenotypic assay is capable of detecting every deficiency, because the various mutations express different molecular characteristics, rendering thrombophilia screening repertoires employing one assay per potential deficiency, of limited effectiveness. Activated protein C resistance (APCR) is more common than discrete deficiencies of antithrombin, protein C, and protein S and also often detected initially with phenotypic assays; however, some centres perform only genetic analysis for factor V Leiden, as this is responsible for most cases of hereditary APCR, accepting that acquired APCR and rare F5 mutations conferring APCR will go undetected if only factor V Leiden is evaluated. All phenotypic assays have interferences and limitations, which must be factored into decisions about if, and when, to test, and be given consideration in the laboratory during assay performance and interpretation. This review looks in detail at performance and limitations of routine phenotypic thrombophilia assays.

Protein C deficiency with venous and arterial thromboembolic events

Protein C (PC) is a key component of the vitamin K-dependent coagulation pathway. It exerts anticoagulant effects by inactivating factors V and VIII. Acquired or inherited PC deficiency results in a prothrombotic state, with presentations varying from asymptomatic to venous thromboembolism. However, there has been an increasing number of reports linking PC deficiency to arterial thromboembolic events, such as myocardial infarction and ischemic stroke. This editorial focuses on the association between PC deficiency and thromboembolism, which may provide some insights for treatment strategy and scientific research.

The thrombotic risk in Cushing's syndrome-questions, answers, and the algorithm to consider in its assessment: part I-thrombotic risk not related to surgery

Introduction

Recently, it has been reported that there is a great diversity in strategies used for thromboprophylaxis in patients with Cushing's syndrome (CS). An aim of this review was to discuss these practices in light of the existing data on the thrombotic risk in patients with CS and guidelines for medically ill patients.

Methods

The four relevant topics and questions on thrombotic risk in CS were identified. The current guidelines on prevention and diagnosis of venous thromboembolism (VTE) were reviewed for the answers. An algorithm to consider in the assessment of the thrombotic risk in patients with CS was proposed.

Results

To address both generic and CS-specific risk factors for VTE, the algorithm includes the stepwise approach consisting of Padua Score, urine free cortisol, and CS-VTE score, with no indication for routine thrombophilia testing in the prediction of an index VTE episode. Having confirmed VTE, selected patients require thrombophilia testing to aid the duration of anticoagulant treatment. The separate part of the algorithm is devoted to patients with ectopic adrenocorticotropic hormone syndrome in whom exclusion of VTE precedes introducing routine thromboprophylaxis to prevent VTE. The cancer-related VTE also prompts thromboprophylaxis, with the possible vessel invasion. The algorithm presents a unifactorial and multifactorial approach to exclude high-bleeding risks and safely introduce thromboprophylaxis with low-molecular-weight heparin.

Summary

Our article is the first to present an algorithm to consider in the thrombotic risk assessment among patients with Cushing's syndrome as a starting point for a broader discussion in the environment. A plethora of factors affect the VTE risk in patients with CS, but no studies have conclusively evaluated the best thromboprophylaxis strategy so far. Future studies are needed to set standards of care.

The clinical and genetic landscape of early-onset thrombophilia in Japan

OBJECTIVES

To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan.

METHODS/RESULTS

Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019).

CONCLUSIONS

We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.

Molecular basis of inherited protein C deficiency results from genetic variations in the signal peptide and propeptide regions

BACKGROUND

Inherited protein C deficiency (PCD) caused by mutations in protein C (PC) gene (PROC) increases the risk of thrombosis. Missense mutations in PC's signal peptide and propeptide have been reported in patients with PCD, but their pathogenic mechanisms, except mutations in R42 residue, remain unclear.

OBJECTIVES

To investigate the pathogenic mechanisms of inherited PCD caused by 11 naturally occurring missense mutations in PC's signal peptide and propeptide.

METHODS

Using cell-based assays, we evaluated the impact of these mutations on various aspects such as activities and antigens of secreted PC, intracellular PC expression, subcellular localization of a reporter protein, and propeptide cleavage. Additionally, we investigated their effect on pre-messenger RNA (pre-mRNA) splicing using a minigene splicing assay.

RESULTS

Our data revealed that certain missense mutations (L9P, R32C, R40C, R38W, and R42C) disrupted PC secretion by impeding cotranslational translocation to the endoplasmic reticulum or causing endoplasmic reticulum retention. Additionally, some mutations (R38W and R42L/H/S) resulted in abnormal propeptide cleavage. However, a few missense mutations (Q3P, W14G, and V26M) did not account for PCD. Using a minigene splicing assay, we observed that several variations (c.8A>C, c.76G>A, c.94C>T, and c.112C>T) increased the incidence of aberrant pre-mRNA splicing.

CONCLUSION

Our findings suggest that variations in PC's signal peptide and propeptide have varying effects on the biological process of PC, including posttranscriptional pre-mRNA splicing, translation, and posttranslational processing. Additionally, a variation could affect the biological process of PC at multiple levels. Except for W14G, our results provide a clear understanding of the relationship between PROC genotype and inherited PCD.

Evaluation of living donors for hereditary liver disease (siblings, heterozygotes)

Living donor liver transplantation (LDLT) is recognised as an alternative treatment modality to reduce waiting list mortality and expand the donor pool. Over recent decades, there have been an increasing number of reports on the use of LT and specifically LDLT for familial hereditary liver diseases. There are marginal indications and contraindications that should be considered for a living donor in paediatric parental LDLT. No mortality or morbidity related to recurrence of metabolic diseases has been observed with heterozygous donors, except for certain relevant cases, such as ornithine transcarbamylase deficiency, protein C deficiency, hypercholesterolemia, protoporphyria, and Alagille syndrome, while donor human leukocyte antigen homozygosity also poses a risk. It is not always essential to perform preoperative genetic assays for possible heterozygous carriers; however, genetic and enzymatic assays must hereafter be included in the parental donor selection criteria in the aforementioned circumstances.