Chapter 4

Question 1

what is the most common cause of thrombocytopenia in children and adults?

Answer 1

IMMUNE aka IDIOPATHIC THROMBOCYTOPENIC PURPURA (ITP)
Autoimmune production of lgG against platelet antigens (e.g., GPIb/IIIa)
Most common cause of thrombocytopenia in children and adults
Autoantibodies are produced by plasma cells in the spleen.

Focus on the name “idiopathic”
This is a diagnosis of exclusion
If nothing else is pathognomonic

Divided into acute and chronic forms

1. Acute form arises in children weeks after a viral infection or immunization; self- limited, usually resolving within weeks of presentation
2. Chronic form arises in adults, usually women ofchildbearing age. May be primary or secondary (e.g., SLE). May cause short-lived thrombocytopenia in offspring since antiplatelet IgG can cross the placenta.

Question 2

what is TTP

Answer 2

thrombotic thrombocytopenia purpura
aka "the terrible pentad"
-adams 13 def
-inc bleeding time and thrombocytopenia
AS WELL AS anemia, neuro sx, renal sx, and fever

-can see schistocytes

Question 3

what insufficiency is more common is HUS?

what insufficiency is more common is TTP?

Answer 3

Renal insufficiency (more common in HUS)-
Thrombi involve vessels of the kidney.

CNS abnormalities (more common in TTP)-
Thrombi involve vessels of the CNS.

Question 4

Bernard-Soulier vs. Glanzmann thrombasthenia

Answer 4

Bernard-Soulier syndrome is due to a genetic GPIb deficiency; platelet adhesion is impaired. Blood smear shows mild thrombocytopenia with enlarged platelets.

Glanzmann thrombasthenia is due to a genetic GP!Ib/IIIa deficiency; platelet aggregation is impaired.

Question 5

what does aspirin and uremia do to platelets?

Answer 5

Aspirin irreversibly inactivates cyclooxygenase; lack of TXA2 impairs aggregation.

Uremia disrupts platelet function; both adhesion and aggregation are impaired.

Question 6

􏰘Tissue thromboplastin activates factor VII (extrinsic pathway).

Subendothelial collagen activates factor XII (intrinsic pathway).

Answer 6

x

Question 7

what are the lab values found in vWF deficiency?

Answer 7

• autosomal dominant with decreased vWF levels bleeding time
• increased PTT; normal PT
• Decreased FVIII half-life (vWF normally stabilizes FVIII)
• however, deep tissue, joint, and postsurgical bleeding are usually not seen.
• Abnormal ristocetin test- Ristocetin induces platelet aggregation by causing vWF to bind platelet GPIb; lack of vWF –> impaired aggregation –> abnormal test.

-Treatment is desmopressin (ADH analog), which increases vWF release from
Weibel-Palade bodies of endothelial cells.

Question 8

Worst case complication of HIIT?

Answer 8

thrombosis!!! destroyed platelets activate remaining platelets

Question 9

what does plasmin do?

Answer 9

Plasmin can:
~Cleaves fibrin
~ Cleaves serum fibrinogen
~Destroys coagulation factors
~Blocks platelet aggregation

a2-antiplasmin inactivates plasmin.

Question 10

how is plasmin overactivation different than DIC?

Answer 10

Laboratory findings OF PLASMIC OVERACTIVATION include:

1. Increased􏰓 PT/PTT since plasmin destroys coagulation factors.
2. increased bleeding time with normal platelet count since plasmin blocks platelet aggregation.
3. Increased fibrinogen split products without D-dimers. Serum fibrinogen is lysed; however, D-dimers are not formed because fibrin thrombi are absent.

** D DIMERS ARE PRODUCTS OF CROSSLINKED FIBRIN; THEREFORE- NO FIBRIN MADE = YOU GET NO D DIMERS **

Treatment is aminocaproic acid, which blocks activation of plasminogen.

Question 11

Cobalamin transfers methyl to homocysteine resulting in methionine.

Lack of vitamin Bl2 or folate leads to decreased conversion of homocysteine to methionine resulting in buildup of homocysteine.

Cystathionine beta synthase (CBS) deficiency results in high homocysteine levels with homocystinuria.

CBS converts homocysteine to cystathionine; enzyme deficiency leads to homocysteine buildup.

Characterized by vessel thrombosis, mental retardation, lens dislocation, and long slender fingers.

Answer 11

X

Question 12

What is the most common inherited cause of hypercoagulable state?

Answer 12

Factor V Leiden is a mutated form of factor V that lacks the cleavage site for deactivation by proteins C and S.
Most common inherited cause of hypercoagulable state

Prothrombin 20210A is an inherited point mutation in prothrombin that results in increased gene expression. Increased prothrombin results in increased thrombin, promoting thrombusformation.