congenital factor XI deficiency

Congenital factor XI deficiency is an inherited bleeding disorder that affects the body’s ability to form stable blood clots. It results from reduced levels or activity of factor XI, a protein that works within the intrinsic arm of the coagulation cascade. The condition can appear in people of any age but often first becomes evident when an affected individual experiences unexpected or prolonged bleeding after surgery, dental work, or injury. It is considered rare, affecting roughly one to nine people in a million worldwide. Severity and symptoms vary widely between individuals, and many people remain unaware of the condition until a hemostatic challenge reveals it.

Most individuals with congenital factor XI deficiency feel healthy day to day, and spontaneous bleeding is uncommon. The hallmark feature is excessive or prolonged bleeding that typically emerges after a trigger such as dental extraction, childbirth, or an accident. Laboratory studies often reveal a prolonged partial thromboplastin time and markedly reduced factor XI activity, which point clinicians toward the diagnosis. Recurrent nosebleeds and heavy menstrual periods are reported in a substantial minority, and some people describe easy bruising or prolonged oozing from minor cuts. Not all individuals experience all features, and the degree of bleeding can range from mild to significant even among family members who share the same genetic change. Factors such as trauma type, concurrent medical conditions, and individual variation in clotting proteins contribute to this broad clinical spectrum.

Congenital factor XI deficiency is caused by pathogenic variants in the F11 gene, which provides instructions for making factor XI. When the gene is altered, factor XI levels drop or the protein produced is dysfunctional, interrupting an important step in blood-clot formation and leading to a bleeding tendency. Multiple inheritance patterns have been reported. In autosomal recessive families, a child must inherit two altered copies of F11—one from each parent—to be affected. This pattern is more likely when parents share a common ancestor, because relatives have an increased chance of carrying the same rare variant. Carrier parents have a 25 percent chance with each pregnancy of having an affected child, and carrier testing may be especially helpful for relatives or couples with shared ancestry. Autosomal dominant inheritance has also been documented, in which a single altered copy of F11 can cause reduced factor XI levels. In that scenario, an affected individual has a 50 percent chance of passing the variant to each child. Even within the same family, the intensity of bleeding (variable expressivity) can differ considerably, meaning some relatives may have only mild issues while others require medical intervention. Genetic counseling is recommended for anyone with the condition or a family history of bleeding disorders to clarify individual and reproductive risks.

Currently, management focuses on preventing and controlling bleeding episodes rather than curing the underlying deficiency. Planning is key: people with known factor XI deficiency typically meet with a hematologist before dental work, surgery, or childbirth to outline a hemostatic plan. During procedures with high bleeding risk, replacement of the missing clotting factor through specialist-recommended products or blood products may be considered, and antifibrinolytic medicines may be used to support clot stability. Day-to-day, individuals are encouraged to alert all healthcare providers to their diagnosis so that any invasive procedure can be managed appropriately. Ongoing care is usually coordinated by a multidisciplinary team led by hematology, and families benefit from genetic counseling to review inheritance, testing options for relatives, and future family planning.

With careful planning and modern medical support, most people with congenital factor XI deficiency lead full, active lives. The overall outlook depends on the severity of factor XI reduction, access to specialized care, and awareness of the condition when procedures or injuries occur. Outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with a hematologist experienced in bleeding disorders as well as a genetic counselor who can guide testing, carrier detection, and family planning discussions.