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KLKB1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

KLKB1 gene

The KLKB1 gene provides instructions for making prekallikrein, a protein involved in blood clotting and the inflammatory response.

Normal Function

The KLKB1 gene provides instructions for making a protein called prekallikrein, which is produced in the liver and circulates in the blood. A molecule called factor XII converts prekallikrein into plasma kallikrein, which in turn activates more factor XII. This interaction is part of the intrinsic coagulation pathway (contact activation pathway), which is involved in the early stages of blood clotting.

The interaction between plasma kallikrein and factor XII also initiates chemical reactions that release a protein called bradykinin. Bradykinin promotes inflammation by increasing the permeability of blood vessel walls, allowing fluids to leak into tissues and causing swelling.

Health Conditions Related to Genetic Changes

Prekallikrein deficiency

At least nine KLKB1 gene mutations have been identified in people with prekallikrein deficiency. This condition generally does not cause health problems and is typically discovered incidentally during blood tests performed for other reasons.

  • Mutations reduce or eliminate functional plasma kallikrein in the blood, impairing the intrinsic coagulation pathway.
  • The condition is usually asymptomatic because the extrinsic coagulation pathway (tissue factor pathway) can compensate for the impaired intrinsic pathway.
  • Either pathway is capable of activating the proteins necessary for the later stages of the blood clotting process.

Genomic Location

The KLKB1 gene is found on chromosome 4.

Frequently Asked Questions

No, prekallikrein deficiency is not associated with an increased risk of thrombosis. In fact, it is generally considered a benign, inherited bleeding disorder with no known thrombotic complications.
Diagnosis is usually made by a coagulation panel that includes a prolonged activated partial thromboplastin time (aPTT) that does not correct with a mixing study. A specific assay measuring prekallikrein activity or a genetic test for KLKB1 mutations can confirm the diagnosis.
Most people with prekallikrein deficiency are asymptomatic, but some may notice mild bruising, easy bleeding after minor cuts, or prolonged bleeding from dental work. Because the extrinsic coagulation pathway often compensates, serious bleeding events are rare.
Patients should inform their healthcare provider about the deficiency. Anticoagulant or antiplatelet medications should be avoided if possible, and local hemostatic measures (pressure, sutures, topical agents) are usually sufficient. In rare cases, a plasma kallikrein concentrate or fresh frozen plasma may be considered, but this is rarely needed.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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