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AA_USMLE_First Aid & Qbank > Heme > Flashcards

Heme Flashcards

1
Q

From what 2 places is vWF derived?

A
  1. Weibel-Palade bodies of endothelial cells

2. α-granules of platelets

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2
Q

___a___ binds sub-endothelial collagen when it is exposed from damage to the endothelial cell wall.

Platelets then bind to its ___b___ receptors to begin the formation of a blood clot.

c) This adhesion of platelets induces a shape change, causing them to degranulate, releasing what 2 mediators?
What are the functions of these 2 mediators?

A

a) vWF
b) GP1b

c)
1. ADP (dense granules) promotes exposure of GPIIb/IIIa receptors on platelets (for further aggregation)
2. TXA2 promotes platelet aggregation & vasoconstriction

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3
Q

Platelets aggregate amongst each other via linking molecule, __a__, binding to their __b__ receptors, forming a weak platelet plug.

A

a) Fibrinogen

b) GPIIb/IIIa

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4
Q

Disorders of Primary Hemostasis primarily present w/ what types of symptoms?

A

Skin & Mucosal Bleeding
- also easy bruising

(i.e. Epistaxis, hemoptysis, GI bleeding, hematuria, menorrhagia)
(intracranial bleeding occurs w/ severe thrombocytopenia)

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5
Q

Intracranial bleeding occurs under what pathologic conditions of primary hemostasis?

A

When there is Severe Thrombocytopenia

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6
Q

Sizes of the 3 types of skin bleeding?

A
  1. Petechiae = pinpoint bleeding
    (usually only occurs w/ thrombocytopenia, not qualitative disorders)
  2. Purpura = >3mm
  3. Ecchymoses = > 1cm
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7
Q

What is the most common cause of Thrombocytopenia in children & adults?

A

ITP

Idiopathic/Immune Thrombocytopenic Purpura

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8
Q

ITP - pathology?

A
  • Autoimmune production of IgG antibodies against platelet antigens (ex: GPIIb/IIIa)
  • Antibodies are produced by the spleen & antibody-bound platelets are consumed by splenic macrophages
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9
Q

ITP - Prognosis?

A
  • Acute form is usually seen in children & is self-limited & usually resolves w/in a few weeks
  • Chronic form usually arises in adults (women of child-bearing age), lasts a bit longer, & may cause short-lived thrombocytopenia in offspring (IgG can cross placenta)
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10
Q

How is PT/PTT affected in Thrombocytopenia?

A

They are Normal

  • these reflect the coagulation cascade, not platelet count (which is primary hemostasis)
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11
Q

ITP - Laboratory Findings?

A
  • ↓ Platelet count (<50 K/μL)
  • Normal PT/PTT
  • ↑ Megakaryocytes on bone marrow biopsy
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12
Q

ITP - Tx?

A

Corticosteroids

  • IVIG if bleeding (distracts splenic macrophages)
  • Splenectomy (refractory cases, last option)
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13
Q

Microangiopathic Hemolytic Anemia - pathology?

A

Pathologic formation of platelet micro thrombi in small vessels

  • shear RBCs as they squeeze by in small vessels
  • uses up platelets → thrombocytopenia
  • Seen in TTP & HUS
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14
Q

Thrombotic Thrombocytopenic Purpura (TTP) - pathology?

A
  • ↓ADAMS TS13 (enzyme), which normally chops up vWF multimers for degradation
  • Leads to abnormal platelet adhesion & micro thrombi formation → ITP
  • Usually seen in adult female w/ acquired autoimmune degradation of ADAMS TS13
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15
Q

2 pathologies that lead to Microangiopathic Hemolytic Anemia?

A

Thrombotic Thrombocytopenic Purpura
&
Hemolytic Uremic Syndrome

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16
Q

HUS - pathology?

A
  • E. coli 0157:H7 produces E. coli verotoxin, which damages endothelial cells →platelet micro thrombi (in kidneys & brain) → Hemolysis → Thrombocytopenia
  • Children get it from undercooked beef
17
Q

HUS - Clinical symptoms?

A
  • Skin & mucosal bleeding
  • Microangiopathic Hemolytic Anemia
  • Fever
  • Renal insufficiency
  • CNS abnormalities

**Same as TTP

18
Q

TTP - Clinical symptoms?

A
  • Skin & mucosal bleeding
  • Microangiopathic Hemolytic Anemia
  • Fever
  • Renal insufficiency
  • CNS abnormalities

**Same as HUS

19
Q

TTP - TX?

A

Plasmapheresis (remove proteins, autoantibodies, from blood)

  • Corticosteroids
20
Q

Abnormal Thrombin time - means what?

A

Fibrinogen Deficiency

DIC

21
Q

In Thrombocytopenia, how do you differentiate between decreased production & increased destruction of platelets?

A

↓ production = ↓Megakaryocytes in bone marrow

↑ destruction = ↑Megakaryocytes in bone marrow

22
Q

Hemophilia A - lab findings?

A
  • ↑aPTT
  • Factor XIII assay (confirmatory)

(Normal BT, PC, PT, TT)

23
Q

Hemophilia B - lab findings?

A
  • ↑aPTT
  • Factor IX assay (confirmatory)

(Normal BT, PC, PT, TT)

24
Q

von Willebrand disease - lab findings?

A
  • ↑aPTT, ↑ Bleeding time
  • vWF assay (confirmatory)

(Normal PC, PT, TT)

25
Q

DIC - lab findings?

A
  • ↑ BT, PT, aPTT, & TT
  • ↓ Platelet count
  • Fibrin & fibrinogen degradation products
26
Q

What molecule links platelets via binding G2b/3a receptors?

A

Fibrinogen

27
Q

Abnormal Ristocetin test means what?

A

vWF deficiency (diminished aggregation)
OR
Bernard-Soulier Disease; ↓ G1b receptors (no agglutination)

28
Q

Clopidogrel - MOA?

A

Inhibits the release of ADP from platelets, thus inhibiting platelet expression of G2b/3a receptors

(ADP normally stimulates expression of G2b/3a receptors)

29
Q

Ticlodipine - MOA?

A

Inhibits the release of ADP from platelets, thus inhibiting platelet expression of G2b/3a receptors

(ADP normally stimulates expression of G2b/3a receptors)
(same as Clopidogrel)

30
Q

Abciximab - MOA?

A

Interferes w/ G2b/3a function

normal function = binding to fibrinogen to bind platelets together

31
Q

Normal function of ADAMSTS13?

A

Cleaves large multimers of vWF that are released from Weibel-Palade bodies into smaller multimers & monomeric units.

The large & ultra-large multimers that are originally released are VERY adhesive & reactive, so they should be broken down upon release.

32
Q

Prostacyclin (PGI2) function in the coagulation cascade?

A

Prostacyclin is a potent inhibitor of platelet aggregation & prevents their deposition on normal vascular endothelium.

It is synthesized by endothelial cells when cAMP levels increase (whereas TXA2 causes ↓cAMP)

33
Q

What is Christmas Disease?

A

Hemophilia B (↓ factor IX)

  • indistinguishable from Hemophilia A, just less common
34
Q

Vitamin K deficiency - heme lab findings?

A

↑ PT & aPTT

35
Q

Classic pentad of TTP?

A

Fever, Microangiopathic hemolytic anemia, Thrombocytopenia, Renal insufficiency, & Neurologic abnormalities

36
Q

Dx?

  • Primary hemostatic bleeding w/ gingival hemorrhages
  • Bleeding into muscles & subcutaneous tissues
  • Hemorrhagic perifollicular hyperkeratotic papules, each papule surrounding a twisting, corkscrew-like hair
A

Scurvy (vitamin C deficiency)

  • also associated w/ a “tea & toast” diet

AA_USMLE_First Aid & Qbank (22 decks)

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