Idiopathic Thombocytopenic Purpura

Question 1

what does ITP stand for?

Answer 1

diopathic thrombocytopenic purpura

also called immune thrombocytopenic purpura

Question 2

what is ITP?

Answer 2

an acquired form of thrombocytopenia in which patients produce antibodies that bind to their own platelets, marking them for destruction in the spleen

the platelet count drops, and eventually there are not enough platelets to participate in normal clotting

Question 3

what is purpura?

Answer 3

large areas of bleeding within the skin

looks like blood big freckles

Question 4

what are the two forms of ITP?

Answer 4

acute and chronic ITP

Question 5

what is chronic ITP?

Answer 5

slow onset with mild symptoms like petechiae, nosebleeds, easy bruising and excessive menstrual flow

bleeding is relatively minor

life threatening bleeding is rare, especially if you’re getting treated

Question 6

what are the types of chronic ITP?

Answer 6

1. primary = unrelated to any known risk factors
2. secondary = occurring in the setting of other conditions like lupus, HIV or hematologic malignancy called chronic lymphocytic leukemia

Question 7

what conditions can cause secondary chronic ITP?

Answer 7

• lupus
• HIV
• hematologic malignancy called chronic lymphocytic leukemia

Question 8

what population is usually effected by chronic ITP?

Answer 8

mostly in adult women under the age of 40

Question 9

what population nis usually effected by acute ITP?

Answer 9

children

and usually happens following a viral illness

Question 10

what is acute ITP?

Answer 10

abrupt onset ITP

sudden appearance of a petechial rash, bruising, or bleeding, the child usually looks and feels well

the disease is self-limiting. With or without treatment, most children completely recover within a few months

Question 11

what’s the pathogenesis of ITP?

Answer 11

patients make antibodies that bind to their own platelets

the antibodies bind to platelet glycoproteins, such as glycoprotein IIb/IIIa

anything covered in antibodies looks like food to macrophages so in ITP the macrophages in the spleen destroy the antibody-coated platelets

Question 12

what is opsonization?

Answer 12

the process of coating cells with antibodies

Question 13

why is the body generating antibodies against its own platelets in ITP?

Answer 13

1. sometimes, the patient has had a recent viral illness, and the antibodies generated to fight the virus just happen to cross-react with the patient’s platelets
2. the patient has a pre-existing autoimmune disease, like lupus, in which normal immune processes have gone awry, and antibodies are made against all sorts of “self-antigens,” including those on platelets
3. idiopathic

Question 14

How do the antiplatelet antibodies damage the platelets in ITP?

Answer 14

They coat (“opsonize”) the platelets, which makes them appear yummy to macrophages in the spleen.

Question 15

what does the blood smear of ITP show?

Answer 15

isolated thrombocytopenia = platelets are decreased in number but everything else is fine!

occasionally, some of the platelets may be larger than normal, but otherwise, the platelets do not appear abnormal

Question 16

what’s the number of platelets in thrombocytopenia?

Answer 16

minor: 100,000 – 149,000/mmˆ3
severe: <10,000/mmˆ3

Question 17

what does the bone marrow in ITP look like?

Answer 17

increased number of megakaryocytes, many of which are smaller than normal, with just a single nucleus instead of the usual multinucleated huge megakaryocytes seen in normal bone marrow biopsies

Question 18

what tests do you do to diagnose ITP?

Answer 18

there are no specific laboratory tests or diagnostic criteria that can be used to prove that ITP is present…

you can’t look for anti-platelet antibodies because the antibody tests have a very low sensitivity so the tests are useless and doctors don’t even do them

Question 19

how do you diagnose ITP?

Answer 19

• patient must have isolated thrombocytopenia
• you also have to show that there isn’t another apparent cause for the thrombocytopenia

ITP is a diagnosis of exclusion

Question 20

what are some other causes of an isolated thrombocytopenia other than ITP?

Answer 20

1. Pseudothrombocytopenia (a falsely low platelet count due to things like an insufficiently anticoagulated specimen)
2. Infection (such as HIV, hepatitis C, and EBV)
3. Hypersplenism (a big spleen can “trap” platelets, making the peripheral count
   appear low)
4. Pregnancy-related thrombocytopenia
5. Medication-related thrombocytopenia

Question 21

what is isolated thrombocytopenia?

Answer 21

low platelets BUT RBC and WBC are totally normal

Question 22

how do you treat ITP?

Answer 22

treatment is typically given to patients with severe bleeding or with really, really low platelet counts like <10,000

1. glucocorticoids (steroids)
2. IV immune globulin
3. platelet transfusions
4. splenectomy if no other treatment works so you can remove the source of platelet destruction

Question 23

what, if present in a patient, would rule out the diagnosis of ITP?

Answer 23

Hb = 9.2 g/dL

to diagnose ITP, the thrombocytopenia must first be isolated meaning there are not any other abnormalities in blood counts, such as a low hemoglobin, which should lead you in a different diagnostic direction