Page 365 - Concise Pathology for Exam Preparation ( PDFDrive )

350 SECTION II Diseases of Organ Systems

Pathophysiology

• Abnormal or deficient VWF
• Synthesis of this macromolecule coded by a gene on chromosome 12
• VWF acts as a carrier of Factor VIII and is required for normal platelet adhesion

Laboratory Diagnosis
• Prolonged BT n mild bleeding, easy bruising, epistaxis and bleeding following minor
procedures
• Factor VIII C assay n levels decreased
• von Willebrand factor immunoassay n levels decreased
• Ristocetin-induced platelet aggregation delayed n ristocetin induces platelet agglu-
tination followed by secondary aggregation and release reaction; this process depends on
binding of VWF to platelet membrane

Q. Write briefly on acquired coagulation disorders.
Ans. Acquired coagulation disorders may result from:
1. Deficiency of vitamin K-dependent factors
(a) Haemorrhagic disease of newborn
(b) Biliary obstruction
(c) Malabsorption of vitamin K
(d) Nutritional deficiency
(e) Drugs:
(i) Coumarins
(ii) Broad spectrum antibiotics
(iii) Cholestyramine
2. Accelerated destruction of coagulation factors
(a) Disseminated intravascular coagulation (DIC)
(b) Fibrinogenolysis (liver disease, thrombolytic agents, tumours postsurgery)
3. Circulating inhibitors of coagulation
(a) Specific inhibitors
(b) Lupus anticoagulant
(c) Antithrombins
(d) Paraproteins
4. Miscellaneous causes
(a) After massive transfusion
(b) After antibiotics and antineoplastic agents
(c) Congenital heart disease, amyloidosis, nephrotic syndrome, Sheehan syndrome,
Gaucher disease and leukaemias

Q. Write briefly on the aetiopathogenesis, clinical features and
laboratory findings in disseminated intravascular coagulation (DIC).

Ans. DIC has the following clinico-haematological features:
Causes

• Obstetric complications
• Abruptio placenta
• Septic abortion/intrauterine death
• Chorioamnionitis
• Amniotic fluid embolism
• Severe eclampsia
• Degenerated H. mole and leiomyomas
• Fetomaternal blood passage

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