Thrombophilia

Thrombophilia is the propensity to develop thrombosis(blood clots) due to an abnormality in the system of coagulation.

Indications

Searching for a coagulation abnormality is not normally undertaken in patients in whom thrombosis has an obvious other cause. For example, if the thrombosis is due to immobilisation after recent orthopedic surgery, it is unlikely that an underlying cause is found.

Conversely, although thrombosis itself may occur in any person, repeated (two or more) unprovoked episodes of thrombosis and unusual sites and types of thrombosis (e.g. Budd-Chiari syndrome) may point towards a coagulation disorder.

Increasingly, habitual abortionis seen as an indication for thrombophilia screening. Up to 20% of women presenting with recurrent pregnancy loss may have a coagulation disorder.

Classification

Thrombophilia can be classified in various forms.

• The most common classification is by the nature of the thrombosis: arterial, venousor combined.
• Crowther & Kelton (2003) propose to classify the abnormality by the molecular deficiency, type I being the (severe) deficiencies of inhibitors, and type II being the less severe elevation of coagulation factors.
• Acquired vs. congenital

Types

Common types:

• Factor V, Leiden type(3% of the population are heterozygousfor FVL).
• Prothrombinmutation (G20210A, 5'UTR).
• High homocysteinelevels due to MTHFRmutation or vitamin deficiency (vitamins B6, B12 and folic acid).
• Antiphospholipid antibodies
  • anticardiolipin antibodiesand/or
  • lupus anticoagulants
• Renal disease(renal loss of antithrombin)

Rare forms:

• Plasminogenand fibrinolysisdisorders.
• Paroxysmal nocturnal hemoglobinuria
• Protein C deficiency.
• Protein S deficiency.
• Antithrombin IIIdeficiency.

Testing

Tests for thrombophilia include prothrombin timeand INR, partial thromboplastin time, thrombin time, fibrinogenlevels, antiphospholipid antibodylevels (IgG- and IgM-anticardiolipin, dilute Russell viper venom time and lupus anticoagulant), protein C, protein Sand antithrombin(both levels and activity), activated protein C resistance (APC resistance), factor V Leidenand prothrombinmutation. Many laboratories add on various other tests, depending on local policy and guidelines.

Reference

• Crowther MA, Kelton JG. Congenital thrombophilic states associated with venous thrombosis: a qualitative overview and proposed classification system. Ann Intern Med 2003;138:128-34. PDF fulltext.PMID 12529095.de:Thrombophilie

fr:Thrombophilie

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Thrombophilia Wikipedia article Thrombophilia.