Platelets Disorders

Question 1

What are the causes of platelets disorders ?

Answer 1

Thrombocytopenia
Defective platelets- acquired (common) or inherited (rare)
Thrombocytosis

Question 2

What are the manifestations related to thrombocytopenia?

Answer 2

Purpura- Cutaneous bleeding
Petechiae- pinpoint skin bleeding
Mucosal bleeding- epistaxis, ecchymosis
Bleeding worsened by platelet inhibitor drugs such as aspirin, NSAIDs

Question 3

What are the causes of thrombocytopenia ?

Answer 3

Artifactual- platelets clumping,satellites
Decreased production
Platelet loss (blood loss)
Increased destruction states (ITP,TTP,DIC)
Splenic sequestration

Question 4

What are some common drugs causing thrombocytopenia ?

Answer 4

Ampicillin
Digoxin
Acetaminophen

Question 5

What is Immune thrombocytopenia purpura (ITP)?

Answer 5

Abnormal antibody production coating platelets and causing accelerated destruction
Causes are idiopathic, collagen vascular diseases, lymphoma
Can be acute or chronic

Question 6

What are the characteristics of acute ITP?

Answer 6

Last less than 6 months 
Childhood illness (2-6 years)
Self limited in most cases

Question 7

What are the characteristics of chronic ITP?

Answer 7

Last longer than 12 months
Adult illness
Require intervention
Affects more females than males

Question 8

What are the lab findings in ITP?

Answer 8

Thrombocytopenia
Increased MPV
Increased size and number of megakaryocytes on bone marrow

Question 9

What is the suggested lab testing in ITP?

Answer 9

HIV screening
Hepatitic C assay
ANA assay

Question 10

How is ITP treated?

Answer 10

Treat for platelets less than 20,000 or dangerous bleeding
Steroids with Rituximab
Refractory therapy: splenectomy, danazol, immunosuppression

Question 11

What are the outcomes from therapy for ITP?

Answer 11

Initial response rates of 66-75%
Initial duration is months or years
Most patients eventually relapse
Consequent therapy has lessened response

Question 12

What is thrombotic thrombocytopenic purpura (TTP)?

Answer 12

Thrombotic microangiopathy caused by deficiency of VWF cleaving protein ADAMTS13
Results in thrombocytopenia, microangiopathic hemolytic anemia and widespread multi organ thrombosis and injury

Question 13

What is hemolytic uremic syndrome (HUS)?

Answer 13

Triad of non Immune microangiopathic hemolytic anemia,thrombocytopenia and acute renal failure
Highly associated with infectious toxins (STEC O157 H7)

Question 14

What are the symptoms of TTP and HUS?

Answer 14

Fever
Anemia
Thrombocytopenia 
Renal disease
Neurologic symptoms 
Fever and neurologic symptoms are absent in HUS

Question 15

What are the lab findings in TTP/HUS?

Answer 15

Thrombocytopenia with increased bleeding time
Normal PT/PTT
Anemia with schistocytes
Increased megakaryocytes in the bone marrow

Question 16

How is TTP/HUS treated?

Answer 16

Plasmapheresis

Corticosteroids

Question 17

What is heparin induced thrombocytopenia (HIT)?

Answer 17

Acquired hyper coagulable state arising from induction of an antibody against the heparin platelet factor 4 site
Onset is 4-10 days after heparin exposure
Very common
2 types: 1- minor clinical event, 2- white clot syndrome

Question 18

What are the clinical manifestations of HIT?

Answer 18

Arterial thrombosis concurrent with venous thrombosis

Caused by heparin or LMW

Question 19

How is HIT diagnosed?

Answer 19

50% or greater reduction in baseline platelet count, even if still in the normal range
Positive assay for heparin associated antibody

Question 20

What are the factors that affect HIT scoring?

Answer 20

Thrombocytopenia
Timing of platelet count fall
Thrombosis or other sequelae
Other causes for thrombocytopenia

Question 21

How is HIT treated?

Answer 21

Stop heparin in any dose, route or form
Anticoagulate with argatroban, lepirudin
Do not initiate coumadin
Avoid platelet transfusion

Question 22

What is post transfusion purpura?

Answer 22

Acquired thrombocytopenia of the allo immune type
Typically occurs 5-15 days after transfusion of RBCs induces an alloantibody against the P1 antigen
Recipient is usually P1 negative, female and multiparous
It is usually severe (<10,000 platelets)
Patient often febrile

Question 23

How is post transfusion purpura treated?

Answer 23

High dose gamma globulin
Plasmapheresis
Steroids

Question 24

What is abnormal pooling of platelets?

Answer 24

AKA splenic sequestration
Occurs with diseases causing splenic enlargement and subsequent pooling
Usually part of pancytopenia
Therapy is dependent on the cause of the splenomegaly

Question 25

What are the qualitative platelets disorders?

Answer 25

Glanzmann’s thrombastenia- absence of IIb/IIIa receptor: platelets can’t stick together
Bernard- Soulier- absence of Ib/V receptor: can’t bind to VWF
Von Willebrand’s disease- lots of bleeding, patient typically female, elevated PTT

Question 26

What are the platelets level for surgical clearance in thrombocytopenia ?

Answer 26

Minor surgery safe if platelets >50,000
Vascular ans neurosurgical procedures require higher and sustained values
Dental procedures safe when>50,000