F XI deficiency is common in the Jewish population where two mutations, the so-called type II (Glu117stop) and type III mutation (Phe283Leu), prevail. Haplotype analysis indicates that both mutations date back to ancestral founders.[12] In a study performed in Israel, the type II mutation was identified only in Iraqi Jews (allele frequency: 0.0167), which are regarded to represent the original Jewish gene pool in the Middle East. In contrast, both mutations were observed with similar allele frequencies in Ashkenazi Jews (0.0217 and 0.0254, respectively), a main segment of Jews that diverged from the original gene pool and began to migrate to Europe at the time of the Roman Empire.[12] Correspondingly, age estimates based on distribution of allelic variants at a flanking microsatellite marker suggest that the type II mutation dates back more than 120 generations, and that the type III mutation appeared later in history.[13] Recently, in French Basques, a novel mutation (Cys38Arg) with an allele frequency of about 0.005 was reported. Haplotype analysis was consistent with an ancestral founder.[14] Two substitutions, Gln226Arg and Ser248Asn, were identified in an African-American family and subsequently also in population-screening studies indicating that these two variants may be very common in individuals of African origin.[15,16] At present, about 80 mutations have been described in different ethnic groups, the majority being reported in single families or as sporadic cases with unknown allele frequency.

Apart from the Jewish population, inherited factor XI deficiency is generally regarded as a rare condition. However, in a study from the U.K., about 5% of patients with bleeding disorders had factor XI deficiency, many with no known Jewish ancestry.[6,7] Moreover, in our experience, the condition is underdiagnosed. Possible reasons include the fact that factor XI deficiency often remains asymptomatic or is only revealed after hemostatic challenge, and that in APTT assays, results for heterozygote patients may be borderline or within the normal



Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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