Disease State-Platelets

What is the mechanism of heparin-induced thrombocytopenia (HIT)?

Antibodies directed against platelet factor 4 (PF-4) and heparin complex.

A laboratory test which can detect the specific decrease in the platelet surface membrane receptor glycoprotein Ib and thus lead to a diagnosis of Bernard Soulier Syndrome (BSS) is:

Flow cytometry

Which of the following statements is false about von Willebrand's disease (vWD)?

Functional vWF molecules usually occur as a monomers or dimers

Laboratory tests which can contribute toward the diagnosis of Glanzmann Thrombasthenia include all of the following EXCEPT

PT and aPTT

All of the following are true of lab results of patients with Glanzmann thrombasthenia EXCEPT?

Severe thrombocytopenia

Which of the following is the cause of thrombotic thrombocytopenic purpura (TTP)?

ADAMTS13 deficiency

Which of the following laboratory results is characteristic for a patient with Von Willebrand disease?

Abnormal platelet aggregation response to ristocetin

Whereas von Willebrand's Disease (vWD) and Bernard-Soulier Syndrome (BSS) are both disorders of platelet adhesion, differences between the two include all of the following except:

VWD is a rare inherited disorder, whereas BSS is a relatively common inherited disorder.

An 18-year-old patient bled profusely following a tooth extraction. She had a history of sporadically increased menstrual bleeding and nose bleeds. The laboratory tests showed: Platelet count of 350 x 109/L PT of 12 seconds PTT of 125 seconds Factor VIII activity of 20% Factor IX activity levels 102% Platelet aggregation studies - normal ADP, collagen and decreased with Ristocetin. What is the most likely cause of this patients bleeding episodes?

Von Willebrand's disease

In essential thrombocythemia, the platelets are usually:

Increased in number and functionally abnorma

An SDS-agarose gel electrophoresis for determining different multimer sizes of von Willebrand factor (vWF) is performed on a group of patients. Which of the following would indicate a patient who does not have von Willebrand Disease (vWD)?

A column which has 11 heavy-staining bands

Glanzmann Thrombasthenia is caused by:

A defect in GPIIb/GPIIIa receptors leading to impaired platelet aggregation.

Which of the following is a mechanism known to cause platelet satellitosis (satellitism)?

An antibody directed against the platelet membrane

A young child is brought in for a clinic visit for bleeding and bruising tendencies. Coagulation screening tests revealed normal PT and APTT levels. The CBC was overall normal with the exception of a low platelet count and giant platelets. Platelet aggregation studies were then ordered with normal responses to all agents except ristocetin which had no response. Which of the following is the disease correlates with these findings?

Bernard Soulier Syndrome

Which of the following is a genetic platelet disorder characterized by giant platelets, abnormal screening tests for platelet function and moderate to severe thrombocytopenia?

Bernard-Soulier syndrome

A low platelet count, along with a low white blood cell count and red blood cell count is most likely caused by:

Bone marrow hypoplasia

Which of the following can cause an automated platelet count to appear to be lower than it actually is?

Both platelet satellitism and platelet clumping

Acute immune thrombocytopenic purpura (ITP) is MOST OFTEN associated with which of these populations?

Children 2 - 6 years of age

Abnormal platelet function seen in patients with Bernard-Soulier Syndrome is caused by which of the following platelet components?

Defective glycoprotein Ib/IX

Which of the following may result in a platelet count of 230.0 X 109/L with a bleeding time of 15 minutes.

Defective platelet function

In which of the following situations would a bone marrow aspirate and biopsy be MOST LIKELY recommended to aid in diagnosis?

Evaluation of unexplained cytopenias

No platelet aggregation response to ristocetin occurs in both Von Willebrand Disease and in Bernard Soulier Syndrome. In VWD, it is a cofactor for Von Willebrand Factor and as a result of deficiency of VWF, ristocetin becomes deficient as well. What is deficient in Bernard Soulier Syndrome to cause no response to ristocetin?

GP Ib/IX/V

A deficiency of platelet receptor IIb/IIIa can be found in which of the following?

Glanzmann Thrombasthenia

The following results were obtained on a patient with a history of mucocutaneous bleeding: PT 12 seconds APTT 26 seconds Bleeding Time 18 minutes Platelet aggregation studies: ADP - abnormal response Thrombin - abnormal response Collagen - abnormal response Ristocetin - normal response Which of the following does this patient seem to have?

Glanzmann Thrombasthenia

A 3-year-old girl was brought to a physician's office because of fever and bacterial-type illness symptoms. Her blood pressure was elevated. Gram stain of peripheral blood shows Gram-negative rods.Hemogram: hemoglobin 9.1g/dL (normal 12.0 - 16.0 g/dL), hematocrit 28% (normal 37 - 48%), MCV 80 fl (normal 86 - 98 fl), RDW 13.1% (normal 11 - 15%), platelets 85.1 X 109/L (normal 150 - 450 X 109/L) WBC 9.9x109/L (normal 4.3 - 10.8 x 109/L). The peripheral blood smear is represented in the photograph. Which of the following is the most likely associated condition?

Hemolytic uremic syndrome (HUS)

A 2-year-old girl, who had been treated with upper respiratory tract infection a few weeks ago, showed multiple bruises and had the following laboratory findings: Hgb = 13.5 g/dLRBC = 3.9 x 1012/LWBC = 8.0 x 109/LPlatelets = 5 x 109/LBone marrow M:E ratio = 3:1Megakaryocytes = increased These results are most suggestive of which condition?

Immune (idiopathic) thrombocytopenic purpura

How does Aspirin (salicylic acid) affect platelet function?

Inhibiting cyclooxygenase

Bone marrow examinations may aid in the diagnosis of:

Leukemia

A cause of thrombocytopenia due to decreased production of platelets is:

Malignant infiltration of the bone marrow

This image is of a peripheral blood smear from a patient with what condition?

May-Hegglin anomaly

Which of the following is a clinical symptom that is associated with thrombocytopenia?

Petechiae

Which of the following is a common clinical symptom that is directly related to thrombocytopenia?

Petechiae

Which laboratory result is the most critical in recognizing heparin-induced thrombocytopenia (HIT)?

Platelet count

Which of the following tests is expected to have a normal result in a patient with type 1 von Willebrand disease?

Platelet count

The cells which release von Willebrand's Factor (vWF) are:

Platelets and endothelial cells

When assessing the RBC morphology on a peripheral blood smear, which would be an expected finding on a patient with thrombotic thrombocytopenic purpura (TTP) ?

Schistocytes

Decrease platelet production can be caused by a lack of or decreased amount of which of the following?

Thrombopoietin

Which of the following conditions is characterized by small clots made up of platelets and large forms of von Willebrand factor?

Thrombotic thrombocytopenic purpura (TTP)

You are analyzing a patient sample in the hematology laboratory when the instrument you use for automatic CBC flags your specimen for having a low platelet count. Upon performing a visual differential of the slide, you notice that there are indeed very few platelets on the slide. You also notice numerous, fragmented red blood cells. Which of the following choices could be associated with the low platelet count and fragmented red blood cells found in this case?

hrombotic Thrombocytopenic Purpura (TTP)