Lecture 19: Thrombocytopenia

Question 1

What is cutoff for thrombocytopenia in cats and dogs

Answer 1

cats: <180k
Dogs: <150k

Question 2

what is the primary cause of pseudothrombocytopenia

Answer 2

platelet clumping

Question 3

platelet counts <___ at risk for spontaneous bleeding

Answer 3

30k

Question 4

platelet counts __-__ at risk of bleeding secondary to trauma or surgery

Answer 4

30-50k

Question 5

Platelet counts >___ risk for hemorrhage is low with trauma or surgery

Answer 5

50k

Question 6

what is cause of inherited macrothrombocytopenia

Answer 6

mutation in B1 tubulin

Question 7

what breeds is macrothrombocytopenia most common in

Answer 7

KCCS, Norfolk, Cairn

Question 8

in macrothrombocytopenia there is an increase in __ and platelet range from __-__

Answer 8

increase mean platelet volume (MPV) and platelet range: 20-150k

Question 9

t or f: dogs with inherited macrothrombocytopenia are at bleeding risk

Answer 9

false

Question 10

what breeds have normal mild to moderate thrombocytopenia usually >80k platelets

Answer 10

greyhounds and sighthounds

Question 11

what are the clinical signs of thrombocytopenia

Answer 11

1. Petechiae or ecchymoses
2. Epistaxis
3. Hematuria
4. Melena or hematochezia

Question 12

What are the 4 mechanisms for thrombocytopenia

Answer 12

1. Sequestration
2. Decreased production
3. Increased consumption/utilization
4. Destruction

Question 13

what is platelet count with decreased production

Answer 13

<50-100k

Question 14

thrombocytopenia due to decreased production are disorders affecting ___in ___

Answer 14

megakaryocytes in BM

Question 15

what would be red flag on CBC for decreased production causing thrombocytopenia

Answer 15

bi or pancytopenia (thrombocytopenia with anemia +/- neutropenia)

Question 16

what are some causes of decreased production leading to thrombocytopenia

Answer 16

1. Infections- FIV, FeLV, parvo, distemper, herpes, histoplasmosis, ehrlichia
2. Neoplasia: lymphoma, leukemia, multiple myeloma
3. Drugs: chemo, methimazole, phenobarbital, estrogen
4. Immune mediated

Question 17

what are 2 broad causes increase consumption leading to thrombocytopenia

Answer 17

disorders with widespread damage to endothelial cells or trigger massive activation of coagulation

Question 18

what are some specific causes of increase consumption of platelets leading to thrombocytopenia

Answer 18

1. Severe inflammatory disorders
2. DIC (very sick)
3. Vasculitis
4. Trauma/bleeding
5. Vascular masses (hemagiosarcoma)

Question 19

what are some other blood work findings supportive of DIC

Answer 19

prolonged PT, PTT, increased FDP or D-dimers, shistocytes, keratocytes

Question 20

what is platelet count when thrombocytopenia is due to sequestration

Answer 20

mild >100k

Question 21

what are some causes of sequestration leading to thrombocytopenia

Answer 21

Anything that causes hepatosplenomegaly
Ex: anesthetic drugs, infections, neoplasia, venous thromboses, splenic torsion, portal hypertension

Question 22

t or f: if you have patient with moderate to severe thrombocytopenia, sequestration is NOT the primary issue

Answer 22

true

Question 23

what is cause of destruction leading to thrombocytopenia

Answer 23

anti platelet antibody formation leading to immune mediated thrombocytopenia

Question 24

what is primary ITP

Answer 24

idiopathic cause of antibody targeting platelets

Question 25

what is secondary ITP

Answer 25

associated with known or suspected antigenic stimulus

Question 26

what is platelet count typically in primary ITP

Answer 26

severe thrombocytopenia <40k, with most cases <20k

Question 27

what is platelet count typically with secondary ITP

Answer 27

mild to severe thrombocytopenia, unlikely <20k

Question 28

what is the most common cause of severe thrombocytopenia in dogs platelets <40k

Answer 28

primary ITP

Question 29

platelet count of <__ suggestive of primary ITP in dogs

Answer 29

20k

Question 30

what other dx should you run if suspicious for primary ITP

Answer 30

1. CBC/chem, UA 2. 4DX SNAP 3. Thoracic rads 4. Abdominal ultrasound 5. Coag testing 6. BM testing

Question 31

what is tx for primary ITP in dogs

Answer 31

1. Prednisone +/- 2nd immunosuppressive 2. Transfusion 3. Omeprazole

Question 32

what are some triggers to add 2nd immunosuppressive agent in tx of primary ITP in dogs

Answer 32

1. >25kg 2. Severe hemorrhage that requires blood transfusion 3. Failure of steroid therapy alone for 7 days 4. Evans syndrome

Question 33

what is prognosis for primary ITP in dogs

Answer 33

good >80% survival

Question 34

what are some negative prognostic indicators for primary ITP in dogs

Answer 34

1. High BUN at admission 2. Melena at admission 3. Evans syndrome 4. Pulmonary/CNS bleeding

Question 35

t or f: primary ITP in cats extremely rare

Answer 35

true

Question 36

T or f: primary ITP is most common cause for severe thrombocytopenia in cats

Answer 36

false

Question 37

what is most common cause of severe thrombocytopenia in cats

Answer 37

bone marrow issue

Question 38

t of : azathioprine good immunosuppressive agent to tx primary ITP in cats

Answer 38

false- never use in cats

Question 39

T or f: always use immunosuppressive agents when tx secondary ITP

Answer 39

false— use when platelets <40k

Question 40

what ar some causes of secondary ITP

Answer 40

Babesia spp, TMS (Dobermans)

Question 41

case ex: 1yr, FS, Egyptian Mau presenting with lethargy, petechiae, platelet count of 37k last week now 11k, no clumping, regenerative. BM cytology showed erythroid hyperplasia and megakaryocytic hyperplasia. What pathomechanism of thrombocytopenia is likely causing this. What is tx

Answer 41

destruction Tx: dexamethasone, pantoprazole, chlorambucil

Question 42

case ex: 10yr, MN, German shepherd dog 2 weeks intermittent lethargy 1 episode of collapse HCT: 29%, regenerative Platelets: 65k Abnormal spleen on palpation- ultrasound showed splenic mass What pathomechanism is likely at play and what is tx

Answer 42

increase consumption Tx: remove splenic mass