Platelet Disorders FA 397 Pathoma 32

Question 1

Immune Thrombocytopenia

Defect:

Causes?

Lab findings?

Tx:

Answer 1

Defect: Autoimmune production of IgG against platelet antigents — GP2b/3a
- antibodies produced by plasma cells in the spleen (IgG– can cross placenta)

Antibody-platelet complex is consumed by splenic macrophages

= THROMBOCYTOPENIA

Causes: Acute in children due to viral infection but usually self limited

In adults it is more chronic – women of child-bearing age primary or secondary to SLE

Lab:  
Low platelet count
High bleeding time
Normal PT/PTT
Increased megakaryoctyes on bone marrow biopsy

Tx: corticosteroids, IVIG, Splenectomy

Question 2

Thrombotic Thrombocytopenia purpura

Defect:

Lab findings?

Clinical?

Tx:

Answer 2

Inhibition or deficiency of ADAMTS 13 (vWF metalloprotease)
-larger multimers lead to abnormal platelet adhesions
= microthrombi
= end up depleting available platelets

Lab:
Thrombocytopenia (low platelet count)
High bleeding time
Normal PT/PTT
Anemia with schiztocytes
Increase megakaryocytes on bone marrow biopsy.

Clinical:

• Skin and mucosal bleeding
• Microangiopathic hemolytic anemia
• Fever
• Renal sufficiency (not that common)
• CNS abnormalities

Plasmapheresis and corticosteroids

Question 3

HUS

Cause:

Lab findings?

Clinical:

Tx:

Answer 3

endothelial damage due to drugs or infection (Ecoli 0157:H7) – children due to undercooked meat

Microthrombi in small vessels

Lab:
Thrombocytopenia (low platelet count)
High bleeding time
Normal PT/PTT
Anemia with schiztocytes
Increase megakaryocytes on bone marrow biopsy.

Clinical:

• Skin and mucosal bleeding
• Microangiopathic hemolytic anemia
• Fever
• Renal sufficiency
• CNS abnormalities (more associated with TTP)

Question 4

Bernard- Soulier syndrome

Defect:

Lab findings?

Answer 4

genetic GPIb deficiency — loss of platelet adhesion

Lab findings:
mild thrombocytopenia with enlarged platelets (are produced more immature)

Question 5

Glanzmann Thrombasthenia

Defect:

Lab:

Answer 5

Genetic GpIIb/IIIa deficiency
Platlete aggregation is impaired

Lab findings:
Normal platelet count, blood smear shows no platelet clumping, increased bleeding time.