HEMATOLOGY, ONCOLOGY, ALLERGY,AND IMMUNOLOGYHemophilia
Hemophilia A (classic hemophilia) and Hemophilia B(Christmas disease)
are X-linked coagulation disorders characterized by a deficiency in factor VIII
and factor IX, respectively. Patients may have mild, moderate, or severe dis-
ease depending on their factor activity.
Treatment is guided by the type of hemophilia, bleeding site, bleeding severity,
and presence or absence of an inhibitor. Patients may develop inhibitor anti-
bodies against replacement factors, limiting their effectiveness and leading to
risk of anaphylaxis during factor replacement in patients with hemophilia B.
Patients with low levels of inhibitors may be treated with factor VIII or IX
replacement by overwhelming the inhibitor. Hemophiliacs with serious bleed-
ing and high inhibitor levels should be treated with factor VII, which serves as
a factor VIII inhibitor bypassing agent.
SYMPTOMS/EXAM
■ Easy bruising, hemarthrosis, hematuria
■ Muscle hematoma, intracranial hemorrhage, retroperitoneal hematoma
DIAGNOSIS
■ Prolonged PTT, normal PT, abnormal factor assay
■ The clotting factor mixing test mixes normal plasma with a patient’s serum.
Under normal circumstances the PTT should normalize. If the PTT remains
prolonged, then the patient’s serum contains an inhibitor.
TREATMENT
■ Factor replacement is required prior to any invasive procedure, including
central line, lumbar puncture, arterial puncture.
■ Tranexamic acid and aminocaproic acid (Amicar) are used to help prevent
clot dissolution in patients with hemophilia.
Hemophilia A
■ Desmopressin (DDAVP)
■ Indicated for mild to moderate hemophilia with minor bleeding
■ Increases plasma factor VIII levels by three- to five-fold in 30 minutes
■ 0.3 mcg/kg IV
■ Factor VIII replacement
■ See Table 9.9 for factor replacement guidelines.
■ Each U/kg of factor VIII raises factor VIII levels by 2%.
■ Units of factor VIII required =weight (kg) ×0.5×(% activity desired−
% intrinsic activity).
■ For those with low concentrations of inhibitors, an increased factor
dose can be given in attempt to overwhelm existing antibodies.
■ Factor VIIa
■ Indicated for patient with high titer inhibitor levels
Hemophilia B
■ See Table 9.9 for factor replacement guidelines.
■ Factor IX replacement
■ Each U/kg of factor IX raises factor IX levels by 1%.
■ Units of factor IX required = weight (kg) × 1 ×(% activity desired −
% intrinsic activity).
■ Factor VIIa
■ Indicated for patient with high titer inhibitor levels
Inhibitors are present in all
patients with acquired
hemophilia and also develop
in about 20% of patients with
inherited hemophilia.Assume the present level of
factor VIII is zero unless it is
previously known.