7/23/2019 Hemophilia B is a Form of Hemophilia

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Hemophilia B is a form of hemophilia (see this term) characterized by spontaneous or prolonged

hemorrhages due to factor IX deficiency. Prevalence is estimated at around 1 in !"!!! males. Hemophilia

primarily affects males" but a symptomatic form of hemophilia B in female carriers (see this term) has also

been described #ith a generally milder clinical picture. In general" onset of the bleeding anomalies occurs

#hen affected infants start to learn to #al$. %he severity of the clinical manifestations depends on the e&tent

of the factor IX deficiency. If the biological activity of factor IX is belo# 1'" the hemophilia is severe and

manifests as freuent spontaneous hemorrhage and abnormal bleeding as a result of minor inuries" orfollo#ing surgery or tooth e&traction (severe hemophilia B* see this term). If the biological activity of factor

IX is bet#een 1' and +'" the hemophilia is moderately severe #ith abnormal bleeding as a result of minor

inuries" or follo#ing surgery or tooth e&traction but spontaneous hemorrhage is rare (moderately severe

hemophilia B* see this term). If the biological activity of factor IX is bet#een + and ,!'" the hemophilia is

mild #ith abnormal bleeding as a result of minor inuries" or follo#ing surgery or tooth e&traction but

spontaneous hemorrhage does not occur (mild hemophilia B* see this term). Bleeding most often occurs

around the oints (hemarthroses) and in the muscles (hematomas)" but any site may be involved follo#ing

trauma or inury. -pontaneous hematuria is a fairly freuent and highly characteristic sign of the disorder.

Hemophilia B is transmitted in an Xlin$ed recessive manner and is caused by mutations in the /0 gene

(X2) encoding coagulation factor IX. 3iagnosis is suspected on the basis of coagulation tests revealing

prolonged blood coagulation times and can be confirmed by specific measurements of factor IX levels. %he

differential diagnosis should include von 4illebrand disease (see this term) and other coagulation anomalies

leading to prolonged blood coagulation times. Prenatal diagnosis is feasible through molecular analysis ofchorionic villus samples. 5oagulation factor assays can also be carried out on venous and umbilical cord

blood samples. %reatment revolves around substitution therapy #ith plasma derivatives or genetically

engineered recombinant alternatives. %reatment may be administered after a hemorrhage (treatment on

demand) or to prevent bleeding (prophylactic treatment). %he most freuent complication is the production

of inhibitory antibodies against the administered coagulation factor. -urgical interventions" most notably

orthopedic surgery" may be carried out but should be conducted in specialized centers. Historically" the

disease course is severe and" left untreated" severe hemophilia B is generally fatal during childhood or

adolescence. Insufficient or incorrect treatment of recurrent hemarthroses and hematomas leads to motor

impairment #ith severe disability associated #ith stiffness" oint deformation and paralysis. Ho#ever" current

treatment approaches no# allo# these complications to be prevented and the prognosis is favorable6 the

earlier the substitutive therapy is received and the more adapted the treatment is to the clinical status of the

patient" the better the prognosis.