Fig. 2 Illustration of factor IX protein domains. Abbreviations: Sig = signal peptide; Pro=propeptide; AP=activation peptide.
Patients who develop inhibitors are more likely to have null mutations such as deletions and nonsense mutations that prevent synthesis of the factor IX protein. Inhibitors are more rarely found in patients where the mutation causes a loss of function, but not complete absence of the factor IX protein.
Hemophilia B Leyden is a rare form of factor IX deficiency that is characterized by a gradual increase in factor IX levels that begins at puberty. This variant has been associated with a number of different point mutations within an androgen-sensitive region of the factor IX promoter (nucleotide — 23 through +13) and several theories have been proposed to explain the recovery seen in such cases.[12'13]
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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.