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Petechiae
are small, flat, red, discrete areas of skin bleeding that are typically <2
mm in diameter. They are non-blanching, nonpalpable, and occur in dependent
areas of the body Purpura results from coalesced petechiae.
Purpura due to vasculitis is usually palpable and may be pruritic, and the distribution does not follow dependent areas. Wet purpura is the most predictive of serious bleeding in individuals with thrombocytopenia.
Bruise (also called ecchymosis) is caused by the subcutaneous accumulation of extravasated blood. The skin is flat, and the color evolves over time from purplish blue to reddish brown to greenish-yellow, reflecting the metabolism (breakdown) of hemoglobin to biliverdin and bilirubin.
Hematoma is a collection of blood in the extravascular space. Hematomas and hemarthroses (joint bleeding) are typical of coagulation factor deficiencies.
Von Willebrand factor
- Glycoprotein
- Synthesized in endothelial cells & megakaryocytes.
- Excessive bruising & prolonged bleeding
- Levels vary with stress; increase with estrogens, vasopressin, GH & adrenergic stimuli.
- Repeat tests at > 2 weeks
- Type O blood normally has the lowest levels
- Platelet levels tend to be normal, PT should be normal.
von Willebrand disease (Diagnosis)
- VWF antigen level VWF:Ag (Quantity of VWF present in plasma; <50 are considered to be low)
- VWF ristocetin cofactor assay Efficacy of this plasma VWF in its ability to bind platelets in the presence of antibiotic ristocetin.
- Measurement of coagulation factor VIII (FVIII:C)
- Ratio of VWF:RCo/VWF:Ag (differentiate VWD type 1 and 2)
