Protein S deficiency is typically an adult-onset hereditary condition that is a result of pathogenic variants in the PROS1 gene. This disorder causes an increased risk of deep venous thrombosis, superficial thrombophlebitis, and pulmonary embolism.
Genetic testing of the PROS1 gene may establish or confirm a diagnosis and help guide treatment and management decisions. Identification of a disease-causing variant would also enable testing and diagnosis of at-risk relatives.
Testing for protein S deficiency is also included in the broader Invitae Hereditary Thrombophilia Panel. Depending on the individual’s clinical and family history, this broader panel may be appropriate and can be ordered at no additional charge.
Protein S deficiency is an adult-onset condition that increases the risk of blood-clot formation. Protein S deficiency may be hereditary and due to pathogenic variants in PROS1, or acquired through hepatic disease or a vitamin K deficiency. This disorder is associated with an increased risk of developing blood clots in deep veins, especially in the legs (deep vein thrombosis), which can lead to the clots breaking off and blocking blood flow in other parts of the body like the lungs (where it would cause a pulmonary embolism). Approximately half of these events are unprovoked (i.e., they are not preceded by such typical transient risk factors as surgery, trauma, immobilization, air travel, pregnancy, or systemic hormonal contraception). Women with protein S deficiency also have an increased risk of miscarriage and other pregnancy complications.
Individuals with a pathogenic variant in both copies of their PROS1 gene can develop a rare, severe form of protein S deficiency that can cause a life-threatening clotting disorder in infants, called purpura fulminans. This causes blood clots to form in the small blood vessels throughout the body, blocking normal blood flow and potentially leading to localized necrosis.
Pathogenic variants in PROS1 are identified in approximately 43% of affected individuals.
Protein S deficiency is inherited in an autosomal dominant pattern.
While most people with protein S deficiency never develop abnormal blood clots, certain factors can increase the risk, including advanced age, surgery, trauma, inactivity, and pregnancy. Having another inherited disorder of blood clotting in addition to protein S deficiency can also influence the risk of abnormal blood clotting.
The lifetime risk for individuals with protein S deficiency of developing thrombosis is 30 times greater than that of the general population.
The prevalence of protein S deficiency is estimated at 3-13 per 10,000 individuals in the general population. Protein S deficiency is present in approximately 1%-3% of individuals presenting with venous thromboembolism.
Analysis of the PROS1 gene may be considered in individuals with the following:
Recommendations on when to test an individual for thrombophilias including protein S have been suggested:
For management guidelines, please refer to:
Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).
Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence in the transcript listed below. In addition, analysis covers the select non-coding variants specifically defined in the table below. Any variants that fall outside these regions are not analyzed. Any specific limitations in the analysis of these genes are also listed in the table below.
Based on validation study results, this assay achieves >99% analytical sensitivity and specificity for single nucleotide variants, insertions and deletions <15bp in length, and exon-level deletions and duplications. Invitae's methods also detect insertions and deletions larger than 15bp but smaller than a full exon but sensitivity for these may be marginally reduced. Invitae’s deletion/duplication analysis determines copy number at a single exon resolution at virtually all targeted exons. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. Certain types of variants, such as structural rearrangements (e.g. inversions, gene conversion events, translocations, etc.) or variants embedded in sequence with complex architecture (e.g. short tandem repeats or segmental duplications), may not be detected. Additionally, it may not be possible to fully resolve certain details about variants, such as mosaicism, phasing, or mapping ambiguity. Unless explicitly guaranteed, sequence changes in the promoter, non-coding exons, and other non-coding regions are not covered by this assay. Please consult the test definition on our website for details regarding regions or types of variants that are covered or excluded for this test. This report reflects the analysis of an extracted genomic DNA sample. In very rare cases, (circulating hematolymphoid neoplasm, bone marrow transplant, recent blood transfusion) the analyzed DNA may not represent the patient's constitutional genome.
|Gene||Transcript reference||Sequencing analysis||Deletion/Duplication analysis|