Thrombocytopenia - What is the Cause?

Author: V. Dimov, M.D.
Reviewer: S. Randhawa, M.D.

62 yo AAF with PMH of metastatic pancreatic CA went for her regular chemoTx course today and was found the have a platelet count of 23. She has a h/o recurrent DVT despite being on Coumadin with INR of 2.9. She has been on Lovenox for DVT prophylaxis for 3 weeks.

PMH:
Patient had a left thigh pain 7 months ago and was diagnosed with DVT. She was started on Coumadin and despite a therapeutic INR she developed a second DVT 1 month later. She was admitted and a CT of the chest was done to R/O PE. CT showed a cystic mass below the left diaphragm. Adenocarcinoma of the pancreas tail with extension to the spleen was found on the explorative laparotomy. Patient has been on chemotherapy since then for 6 months. Her C-19-9 level was initially high (44) but went down to 8.


C-19-9 Levels

Her platelet count was 400 one month ago, Lovenox was started and 2 weeks later the platelets dropped to 200. Several days later the platelet count was just 23.

She reported a mild nosebleed the day before the admission and bleeding gums when tooth brushing for 2-3 days.

What is going on?
HIT - Heparin Induced Thrombocytopenia vs. platelet clumping.
Patient is having Trousseau syndrome so she need anticoagulation.
Unfortunately Coumadin is effective in only 9-19% of these patients. The best solution for home use seems to be Lovenox SQ.
But Lovenox can cause HIT.

There are 2 forms of HIT:
- Type I starts within 5 days of Heparin Tx and the platelet count is >100
- Type II starts 5-10 days of Heparin Tx and the platelets drop <100.>What to do?
Repeat CBC

Order antiplatelet antibodies - HIT antibody panel is the correct name.

Start Argatroban for suspected HIT. Patients with HIT have an increased risk for both bleeding and thrombosis. Argatroban is a thrombin inhibitor than prevents the thrombosis in HIT.

What happened?
6U of platelets were transfused.
Repeated platelet count showed an increase to 123.


HIT vs ChemoTx induced thrombocytopenia

Argatroban was already started and PTT was adjusted to 50-70s.
INR increased to 2.24 but Fibrinogen was 325 and FSP less than 5.

Final Diagnosis:
Chemotherapy induced thrombocytopenia. That was an unlikely cause initially because patient was receiving the same chemotherapy for 6 months.

Argatroban was stopped and Lovenox was restarted.

What did we learn from this case?
Always repeat the CBC when having low platelet count.
If platelet count increases after a platelet transfusion (always a six-pack = 6U) this rules out an immune process like ITP or HIT.

HIT is a clinical diagnosis. You don't wait for result of the platelet antibody test because it takes a long time.

You have to stop ALL forms of heparin in HIT. It usually takes more than a week for the platelets to increase.

Argatroban is the drug of choice for HIT.

When do we transfuse platelets?
If platelet count is around 20 or there is bleeding.

Does Trousseau syndrome depend on the TU size?
Yes. Usually patients with wide spread metastatic malignancies develop Trousseau syndrome.

Published: 02/11/2005