Platelets Abnormalities

Question 1

What are the clinical findings in patients with either thrombocytopenia or platelets dysfunction ?

Answer 1

Petechiae
Ecchymoses
Epistaxis
Menorrhagia

Question 2

What are the general classes of platelets disorders?

Answer 2

Thrombocytopenia
Thrombocytosis
Defective function

Question 3

What are the causes of thrombocytopenia ?

Answer 3

Decreased production
Decreased survival
Sequestration
Dilution

Question 4

What are the causes of thrombocytosis ?

Answer 4

Reactive

Neoplastic

Question 5

What are the causes of defective function ?

Answer 5

Defective adhesion
Defective aggregation
Defective secretion 
Liver disease
Uremia
Drug effect

Question 6

What are the inherited platelets abnormalities ?

Answer 6

May-Hegglin anomaly
Bernard-Soulier syndrome
Thrombocytopenia with absent radii 
Wiskot-Aldrich syndrome
Glanzman thrombasthenia

Question 7

What are the characteristics of May-Hegglin anomaly?

Answer 7

Autosomal dominant 
Large platelets 
Dohle bodies in leukocytes
Normal platelet function
Patient not prone to bleeding

Question 8

What are the characteristics ofBernard-Soulier syndrome?

Answer 8

Autosomal recessive
Bleeding is due to defective adhesion of platelets to subendothelial collagen after vascular injury
Secondary to deficiency of GPIb complex
Platelets aggregate with all agonists except on ristocetin

Question 9

What are the characteristics with absent radii (TWAR or TAR)?

Answer 9

Autosomal recessive maybe
Thrombocytopenia with normal platelet morphology but abnormal function
Decreased megakaryocytes
Absent radii, normal thumbs
Presentation at birth

Question 10

What are the characteristics Wiskott-Aldrich syndrome?

Answer 10

X-linked recessive
Variable expression, often with IgM deficiency
Thrombocytopenia with small platelets
Decreased platelet survival

Question 11

What are the characteristics of Glanzman thrombasthenia?

Answer 11

Autosomal recessive
Bleeding due to defective platelet aggregation caused by deficient GPIIb/IIIa
Normal platelet count and morphology
Only react to ristocetin

Question 12

What is primary immune thrombocytopenic purpura?

Answer 12

Mild to severe bleeding disorder
Severe thrombocytopenia 
Can be acute or chronic
Normal physical examination  other than signs of mucocutaneous hemorrhage 
No hepatosplenomegaly

Question 13

What are the characteristics of secondary immune thrombocytopenic purpura ?

Answer 13

Indistinguishable from primary
Occurs in the setting of systemic autoimmune disease
Greater tendency to remain chronic or recur
Diagnosis of either kind is by exclusion

Question 14

What are the characteristics of RBC fragmentation syndromes with thrombocytopenia?

Answer 14

Mechanical destruction of circulating RBCs with formation of schistocytes

Question 15

What are the causes of RBC fragmentation syndromes with thrombocytopenia ?

Answer 15

Disseminated intravascular coagulation (DIC)
Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS)
Mechanical heart valves

Question 16

What are the DIC common causes?

Answer 16

Obstetric complications
Infections of all types
Intravascular hemolysis
Snake bites
Leads to consumptive coagulopathy and bleeding diathesis

Question 17

What are the lab findings of DIC?

Answer 17

PT, PTT, TT usually prolonged
Fibrinogen decreased
Thrombocytopenia 
D-dimer, FDP are elevated 
Schistocytes usually seen on peripheral smear

Question 18

What are the characteristics of TTP/HUS?

Answer 18

Destructive thrombocytopenia and diffuse microvascular occlusion by platelet( not fibrin) thrombi
Due to endothelial damage and excessive platelet clumping
Coagulation tests are usually normal

Question 19

What is the clinical features of TTP?

Answer 19

Severe thrombocytopenia
Microangiopathic hemolytic anemia
Neurologic dysfunction
Fever

Question 20

What are the diagnostic features to suggest TTP?

Answer 20

Schistocytosis
Thrombocytopenia 
Increased LDH
Definitive testing for ADAMTS-13
May not be available at time of diagnosis, should treat emergently based on clinical signs/symptoms and above findings

Question 21

How to treat TTP?

Answer 21

Emergent plasma apheresis

Do not treat with platelets

Question 22

What are the characteristics of HUS?

Answer 22

Microangiopathic hemolytic anemia
Acute renal failure
Thrombocytopenia
Prodrome of bloody diarrhea, abdominal pain, nausea and vomiting
Treatment is dialysis and supportive therapy
No association with ADAMTS-13

Question 23

What are the 2 main types of HUS?

Answer 23

Primary- rare, due to complement gene mutations and antibodies to complement
Secondary- most common, due to infection (Shiga toxin, HIV), drug toxicity

Question 24

What is the most common STEC- associated HUS?

Answer 24

Common mode is contaminated hamburger

Question 25

What are the 2 types of heparin induced thrombocytopenia (HIT)?

Answer 25

Type 1: non immune- occurs rapidly after heparin administration, caused by direct platelet aggregating effect of heparin
Type 2: immune- occurs within 5-14 dayss after beginning heparin caused by antibodies to a complex of heparin and low molecular weight proteins

Question 26

What is the most common cause of drug induced platelet dysfunction ?

Answer 26

Aspirin
Inhibits cyclooxygenase
Impairs platelet aggregation
No effects on coagulation cascade