Alternative spelling
Factor V Leiden
Introduction/Definition
Factor 5 Leiden, also known as APC resistance, is a disease that affects the body’s so-called coagulation system. The coagulation system ensures that when an injury occurs, the blood coagulates quickly, the bleeding is stopped and the wound can heal. In addition to the blood platelets (thrombocytes), there is another system that ensures that the blood coagulates.
The so-called factor 5 is a certain protein that is mainly responsible for the course of blood clotting. Factor 5 disease is a mutation in a gene that is responsible for the expression of this factor. Due to this mutation, the factor is still present but can no longer be cleaved by the so-called “activated protein C”.
The activated protein C, or APC for short, normally ensures that blood clotting is not too fast and strong by splitting factor 5 and thus rendering it ineffective. However, due to the mutation, factor 5 is resistant to protein C, which results in increased clotting. Increased blood coagulation triggered by this mutation is a very common cause of what is known as thrombosis, i.e. a blood clot.
Normally, blood clotting should only occur if a vessel is damaged and needs to be closed. However, the disease can cause the blood to clot even without a damaged vessel wall, thus forming a blood clot. For this reason, an existing factor 5 condition is considered a significant risk factor for the formation of such a blood clot.
Frequency
Factor 5 Leiden is the most common genetic cause leading to an increased probability of developing a blood clot. In total, about 2-15% of the European population is affected by the disease. Approximately 10% of the people affected by Factor 5 Leiden are homozygous. This means that both genes, which contain the information for the expression of the protein, are affected by the mutation. The remaining 90% are heterozygous and therefore have only one mutated gene.
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