Factor XI deficiency

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Factor XI deficiency is a disorder that can cause abnormal bleeding due to a shortage (deficiency) of the factor XI protein, which is involved in blood clotting. This condition is classified as either partial or severe based on the degree of deficiency of the factor XI protein. However, regardless of the severity of the protein deficiency, most affected individuals have relatively mild bleeding problems, and some people with this disorder have few if any symptoms. The most common feature of factor XI deficiency is prolonged bleeding after trauma or surgery, especially involving the inside of the mouth and nose (oral and nasal cavities) or the urinary tract. If the bleeding is left untreated after surgery, solid swellings consisting of congealed blood (hematomas) can develop in the surgical area.

Other signs and symptoms of this disorder can include frequent nosebleeds, easy bruising, bleeding under the skin, and bleeding of the gums. Women with this disorder can have heavy or prolonged menstrual bleeding (menorrhagia) or prolonged bleeding after childbirth. In contrast to some other bleeding disorders, spontaneous bleeding into the urine (hematuria), gastrointestinal tract, or skull cavity are not common in factor XI deficiency, although they can occur in severely affected individuals. Bleeding into the muscles or joints, which can cause long-term disability in other bleeding disorders, generally does not occur in this condition.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Most cases of factor XI deficiency are caused by mutations in the F11 gene, which provides instructions for making the factor XI protein. This protein plays a role in the coagulation cascade, which is a series of chemical reactions that forms blood clots in response to injury. After an injury, clots seal off blood vessels to stop bleeding and trigger blood vessel repair.

Mutations in the F11 gene result in a shortage (deficiency) of functional factor XI. This deficiency impairs the coagulation cascade, slowing the process of blood clotting and leading to the bleeding problems associated with this disorder. The amount of functional factor XI remaining varies depending on the particular mutation and whether one or both copies of the F11 gene in each cell have mutations. However, the severity of the bleeding problems in affected individuals does not necessarily correspond to the amount of factor XI in the bloodstream, and can vary even within the same family. Other genetic and environmental factors likely play a role in determining the severity of this condition.

Some cases of factor XI deficiency are not caused by F11 gene mutations. In these cases, the condition is called acquired factor XI deficiency. It can be caused by other disorders such as conditions in which the immune system malfunctions and attacks the factor XI protein. Because factor XI is made primarily by cells in the liver, acquired factor XI deficiency can also occur as the result of severe liver disease or receiving a transplanted liver from an affected individual. In addition, approximately 25 percent of people with another disorder called Noonan syndrome have factor XI deficiency.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Severe factor XI deficiency is passed down in an autosomal recessive pattern, which means both copies of the F11 gene in each cell have mutations. The parents of these individuals each carry one copy of the mutated gene and have partial factor XI deficiency; they rarely show severe signs and symptoms of the condition.

In some families, this condition is inherited in an autosomal dominant pattern, which means one copy of the altered F11 gene in each cell is sufficient to cause the disorder. In these cases, an affected person has one parent with the condition.

The acquired form of factor XI deficiency is not inherited and does not run in families.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Factor XI deficiency is estimated to affect approximately 1 in 1 million people worldwide. The severe deficiency disorder is much more common in people with central and eastern European (Ashkenazi) Jewish ancestry, occurring in about 1 in 450 individuals in that population. Researchers suggest that the actual prevalence of factor XI deficiency may be higher than reported, because mild cases of the disorder often do not come to medical attention.

Which doctor should you see?

The suggested department for discussing Factor XI deficiency is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.