Case 35 + ITP

Question 1

What is the pathophysiology of immune thrombocytopenic pupura?

Answer 1

• autoimmune disorder w/ accelerated platelet destruction via phagocytosis of antibody coated platelets by the reticuloendothelial system (RES) in spleen, liver and bone marrow
• autoantibodies (mainly IgG) against common platelet glycoproteins and, therefore, cross-react with allogeneic platelets

Question 2

What are causes of increased platelet destruction?

Answer 2

• immune mediated: autoimmune, alloimmune, drug induced
• non-immune mediated: endotoxemia or exotoxemia, hemophagocytosis, DIC, associated with fragmentation hemolysis, artificial surfaces, misc

Question 3

What is the differential dx of decreased platelet count due to decreased production? What do you see in blood smear?

Answer 3

• aplastic anemia
• acute leukemia
• myelodysplasia
• Chemo Rx
  smear: small platelets, decreased MEGs

Question 4

What is the differential dx of decreased platelet count due to increased destruction? What do you see in blood smear?

Answer 4

• ITP
• fragmentation hemolytic anemia
• sepsis
  smear: big platelets, increase MEGs

Question 5

What are the causes of fragmentation hemolytic anemia with thrombocytopenia?

Answer 5

Mechanical valves and/or  paravalvular cardiac “leaks”
Disseminated intravascular coagulation
Thrombotic thrombocytopenia purpura
Hemolytic uremic syndrome
Multifocal endothelial disease
     vasculitis
     pre-eclampsia and eclampsia

Question 6

What is the differential dx of decreased platelet count due to ineffective production? What do you see in blood smear?

Answer 6

• megaloblastic anemia
• myeloproliferative disease
• myelodysplasia
• ITP
  smear: variable MPV

Question 7

What is the differential dx of decreased platelet count due to redistribution? What do you see in blood smear?

Answer 7

• big spleen

- due to portal hypertension, storage disease or associated with marrow disorder

Question 8

What are causes of thrombocytopenia secondary to decreased total thrombopoiesis?

Answer 8

Marrow infiltration or replacement
Chemotherapy; irradiation
Aplastic anemia
Myelodysplasia
Certain drugs or alcohol
Hereditary thrombocytopenia

Question 9

What are treatments of ITP?

Answer 9

• Steroids
• IV IgG
• Anti-Rh D
• Splenectomy
• other drugs…like vincristine, azathioprine

Question 10

What is the difference between acute and chronic ITP?

Answer 10

Acute:
children 2-6
abrupt onset bleeding
hemorrhagic bullae in mouth present in severe cases
platelet ct is low
Eos and lympocytosis
duration: self limiting, 2-24 weeks, spontaneous remission

Chronic:
adults >50
more females than males
insidious onset of bleeding
hemorrhagic bullae usually absent
platelet ct low
Eos and lympocytosis uncommon
lasts months to years

Question 11

How do you diagnose ITP?

Answer 11

It is a diagnosis of exclusion
CBC is normal except isolated thrombocytopenia
Normal exam except signs of bleeding
secondary ITP: can be due to autoimmune disorders
must rule out thrombocytopenia due to infections: HIV, H pylori, hep C