Bleeding disorders
Prolonged aPTT and normal PT (INR) suggest an intrinsic pathway defect. Deficiencies of factor XII, prekallikrein, or high molecular weight kininogen all cause a prolonged aPTT without clinical bleeding. Prolonged aPTT with bleeding can occur in congenital or acquired von Willebrand disease and isolated deficiencies of factors VIII, IX, and XI. Antiphospholipid antibodies (lupus inhibitor) cause prolonged aPTT with thromboses rather than bleeding.
Mixing studies that mix the patient’s plasma in a 1:1 ratio with normal plasma can help differentiate between a factor deficiency and an inhibitor as the cause of the prolonged aPTT. Factor deficiencies are corrected during a mixing study, resulting in normalization of the clotting time; while the presence of an inhibitor will prevent correction of the clotting time. This patient’s bloody diarrhea resolved quickly with antibiotic therapy and is unlikely to have caused her prolonged aPTT. She should have a mixing study performed with further evaluation based on the results.
- Intrinsic bleeding disorder
- prolonged PTT
- hemophilia A(8)/B: nl PT, bleeding time, plt count
- replace with DDAVP and aminocaproic acid for hemophilia A
- can also give factor 8
- vWF: increased PTT and bleeding time
- riscocetin test for diagnosis
- DDAVP and aminocaproic acid
- Extrinsic bleeding disorder
- prolonged PT/INR
- vitamin K, coumadin: 2, 7, 9, 10, C, S
- both intrinsic and extrinsic. Factor 7 shortest half life, so PT goes up first
factor 5 leiden
vWF
Acquired coagulation factor inhibitors
| Hemoglobin | 12.5 g/dL |
|---|---|
| Platelet count | 240,000/mm3 |
| PT | 12 seconds |
| aPTT | 58 seconds |
The coagulation studies reveal a normal PT and a prolonged aPTT, which is indicative of an intrinsic pathway disorder and is the typical pattern seen in patients with hemophilia A and B, von Willebrand disease, and certain acquired disorders. Because the X-linked recessive hemophilias are rare in female patients and this woman has no prior history of bleeding suggestive of von Willebrand disease, her bleeding disorder is most likely the result of an acquired coagulation factor inhibitor. Examples of coagulation factor inhibitors include antiphospholipid antibodies (which cause thrombosis) and inhibitors of factors VIII, IX, and XI. Antibodies to factor VIII (''acquired hemophilia'') can result in potentially severe bleeding, and can occur independently or be associated with malignancy, pregnancy, lymphoproliferative disorders, or rheumatic disease.