Question: What is (are) Factor XI deficiency ?
Answer: Factor XI deficiency is a bleeding disorder that interferes with the body's clotting process. As a result, people affected by this condition may have difficulty stopping the flow of blood following dental extractions, trauma or surgery. Women with factor XI deficiency may also experience heavy menstrual periods or heavy postpartum bleeding. Within affected people and their families, highly variable bleeding patterns occur, and bleeding risk can not be predicted by the level of factor XI (a clotting factor) in the blood. Although the condition can affect people of all heritages, it is most common in people of Ashkenazi Jewish descent. Most cases of factor XI deficiency are inherited and caused by changes (mutations) in the F11 gene. The condition is generally inherited in an autosomal recessive manner; however, it may follow an autosomal dominant pattern in some families. Treatment is often only recommended during periods of high bleeding risk (i.e. surgery) and may include fresh frozen plasma and/or antifibrinolytics (medications that improve blood clotting). Factor XI concentrates may be available for factor replacement in some countries.
Source: GARD

Question: What are the symptoms of Factor XI deficiency ?
Answer: What are the signs and symptoms of Factor XI deficiency? The Human Phenotype Ontology provides the following list of signs and symptoms for Factor XI deficiency. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormal bleeding - Autosomal dominant inheritance - Autosomal recessive inheritance - Prolonged partial thromboplastin time - Reduced factor XI activity - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD