Definitions
a group of disorders of the von Willebrand factors. The most common hereditary coagulation abnormality
Pathophysiology
- vWF is a large, multicentric protein stored in platelets & endothelial cells
- vWF mediates the adhesion of platelets to sites of vascular injury via platelet glycoprotein Ib
- von Willebrand disease may caused by congenital absence of vWF or abnormalities in its structure or function
- vHF also function as a carrier protein for coagulation factor VIII, protecting it from rapid clearance, the absence of vWF creates a secondary deficiency of factor VIII
Classification
Epidemiology
affects 1 in 200-500 children (1-3% of the general population)
M:F=1:1
all racial groups are affected
Presentation
delayed bleeding
superficial bleeding due to failure to form a platelet plug
- skin: petechiae, purpura, easy bruising
- mucous membrane : gingival bleeding, epistaxis, GI bleeding
- Menorrhagia
Post-op bleeding
Investigation
detailed pt and family hx
FBC- thrombocytopenia, PT and aPTT may be normal
Suspect vWF disease if prolong PTT
Bleeding time prolong- measured via PFA-100 (Platelet Function Assay)
vWF assays:
- Ristocetin co-factor assay: test vWF binding to platelets
- vWF antigen level
- vWF may be affected by many conditions (inflammation, pregnancy, OCP. thyroid status, blood type, stress, age, diabetes, malignancy)
- factor VIII activity- decreased
- multimeric analysis
Management
Desmopressin (DDAVP)
- induce the release of vWF
- treatment of choice in bleeding episodes, in type 1
- cause 2 to 4 fold increase in vWF and factor VIII within 15-30mim
- variable response in type 2
- contraindicated for type 2B - worsens thrombocytopenia
- ineffective for type 3
Epistaxis- controlled by local pressure and DDVAP
OCP for menorrhagia
DDVAP and antifibrinolytic agent (aminocaproic acid) before laceration repair/tooth extraction and 7-10 days onward
Plasma-derived vWF for severe bleed
all pt shoud avoid aspirin-containing products
a group of disorders of the von Willebrand factors. The most common hereditary coagulation abnormality
Pathophysiology
- vWF is a large, multicentric protein stored in platelets & endothelial cells
- vWF mediates the adhesion of platelets to sites of vascular injury via platelet glycoprotein Ib
- von Willebrand disease may caused by congenital absence of vWF or abnormalities in its structure or function
- vHF also function as a carrier protein for coagulation factor VIII, protecting it from rapid clearance, the absence of vWF creates a secondary deficiency of factor VIII
Classification
| Type 1 (60-80%) | reduced no. of vWF, function & structures are normal most have normal life Trouble following surgery, bruising, menorrhagia |
| Type 2 (20-30%) | qualitative defect, normal level of vWF Has multiple variants: 2A: small multimer, low ristocetin co-factor 2B: gain of function defect. rapid clearance of platelets and large vWF multimers. Thrombocytopenia may occur 2M:reduced RICOF 2N (normandy): binding deficiency of vWF to factor VIII |
| Type 3 | most severe homozygous for the defective gene no detectable vWF low factor VIII hemarthoses, may resemble hemophilia |
Epidemiology
affects 1 in 200-500 children (1-3% of the general population)
M:F=1:1
all racial groups are affected
Presentation
delayed bleeding
superficial bleeding due to failure to form a platelet plug
- skin: petechiae, purpura, easy bruising
- mucous membrane : gingival bleeding, epistaxis, GI bleeding
- Menorrhagia
Post-op bleeding
Investigation
detailed pt and family hx
FBC- thrombocytopenia, PT and aPTT may be normal
Suspect vWF disease if prolong PTT
Bleeding time prolong- measured via PFA-100 (Platelet Function Assay)
vWF assays:
- Ristocetin co-factor assay: test vWF binding to platelets
- vWF antigen level
- vWF may be affected by many conditions (inflammation, pregnancy, OCP. thyroid status, blood type, stress, age, diabetes, malignancy)
- factor VIII activity- decreased
- multimeric analysis
Management
Desmopressin (DDAVP)
- induce the release of vWF
- treatment of choice in bleeding episodes, in type 1
- cause 2 to 4 fold increase in vWF and factor VIII within 15-30mim
- variable response in type 2
- contraindicated for type 2B - worsens thrombocytopenia
- ineffective for type 3
Epistaxis- controlled by local pressure and DDVAP
OCP for menorrhagia
DDVAP and antifibrinolytic agent (aminocaproic acid) before laceration repair/tooth extraction and 7-10 days onward
Plasma-derived vWF for severe bleed
all pt shoud avoid aspirin-containing products
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