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Clin Med - Hematology > Platelet Disorders > Flashcards

Platelet Disorders Flashcards

1
Q

What are the signs and symptoms of platelet bleeding (i.e., primary hemostasis)?

A
  • mucouos membrane bleeding
  • epistaxis
  • prolonged oozing from minor wounds
  • brusing
  • menorrhagia
  • abnormal intraoperative bleeding
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2
Q

What is thrombocytopenia?

A

low platelet counts

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3
Q

What is a failure of secondary hemostasis?

A
  • bleeding from large vessels
  • subcutaneous hematomas
  • hemarthroses
  • intramuscular hematomas

This is a more “coagulation factor deficiency” picture

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4
Q

What are some signs of congenital thrombocytopenia?

A
  • umbilical cord stump bleeding
  • bleeding after circumcision that won’t stop
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5
Q

When you see bruising on a person with suspected thrombocytopenia, what distinguishes it from ordinary bruising?

A
  • indurated (hardened)
  • found in locations where simple trauma bruises are unlikely (e.g, abdomen)
  • sometimes accompanied by petechiae
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6
Q

What are the etiologies of thrombocytopenia?

A

Poor platelet production

  • bone marrow failure
  • infections
  • drugs (sulfa)
  • nutritional disorders (B12, folate)
  • inherited

Increased destruction of platelets

  • splenomegaly
  • non-immune mediated (DIC, HUS)
  • immune-mediated platelet destruction
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7
Q

What do normal platelets look like?

A
  • purple color
  • small (much smaller than RBC)
  • little fuzzy granulations
  • count and multiply in a field by 10k to get total
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8
Q

What is immune thrombocytopenia (ITP)?

A

immune system mediated destruction of platelets.

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9
Q

What do the practice guidelines from ASH 2011 say about treatment of ITP?

A
  • mild symptoms (i.e., no “wet” bleeding) can be treated with observation alone
  • First line treatment includes corticosteriods, IVIG or anti-D immunoglobin
  • Adults: consider for platelet less than 30x109/L try corticosteriods first, IVIG if rapid or IVIG/Anti-D if you can’t do steroids
  • Kids: probaby will use IVIG/Anti-D FIRST as corticosteroids can MASK underlying Leukemia and hide the diagnsosis from you.
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10
Q

What are the pratical considerations in treating ITP?

A
  • no bright line rules for platelet levels
  • Individualize decisions based upon:
    • patient age (little people are dangerous)
    • clincal symptoms
    • platelets
    • parent/your concern
    • access to medical care (ER)
  • Patients at high risk of significant bleeding should be treated and monitored
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11
Q

What are the symptoms of TTP?

A
  • Note: Rare (congenital < acquired)
  • “Classic” Pentad: thrombocytopenia; microangiopathic hemolytic anema; fluctuating neurological signs; renal impairment; fever.
  • Most patients present WITHOUT the full pentad
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12
Q

How do you diagnose TTP?

A
  • ADAMTS13 below normal range is definitive
  • Normal (<5-10%)
  • Positive ADAMTS13 inhibitor = usually acquired
  • Negative ADAMTS13 inhibitor = indicates congenital TTP (Upshaw-Schulman Syndrome)
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13
Q

What does ADAMTS-13 Do?

A
  • It is an enzyme that cleaves von Willebrand multimers
  • It is essential to prevent excessive clot formation
  • low ADAMTS-13 causes multimers to form webs in vessels
    • RBC’s get sheared causing shistocytes
    • platelets get caught in the webs, reducing their numbers
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14
Q

What is Hemolytic Uremic Syndrome (HUS)?

A

A disease that causes microangiopathic hemolytic anemia; thrombocytopenia; and renal impairment (predominant)

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15
Q
  • What is the most common cuase of HUS?
A
  • shiga-toxin producing E. Coli (STEC)

absence of this classified as atypical (aHUS)

  • ​leads to uncontrolled activation of the complement system
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16
Q

What genetic mutation is commonly seen in patients that acquire aHUS?

A
  • 60% have mutation in genes that protect us from complement activation (Factor H - CFH) and I (CFI)
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17
Q

Who is most likely to get HUS?

A
  • Manifests in all ages (note that this is NOT what PPP says)
  • especially in adolescents and adults
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18
Q

What is the threatment for HUS?

A
  • Primarily supportive
  • transfusions may be required for anemia
  • platelet transfusion only resereved for severe bleeding
  • dialysis as need for renal
  • watch fluid load
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19
Q

What is the prognosis for people with HUS?

A
  • Generally favorable - renal recovery
  • hematologic manifestations typically resolve 1-2 weeks
20
Q

What is the treatment for aHUS?

A
  • Plasma exchange
  • Eculizamab - MAb to complement factor C5
    • blocks complement activation
21
Q

What is the prognosis for aHUS?

A

Compared with HUS, prognosis is much poorer. Chronic relapsing course is common and outcome overall is poorer.

22
Q

What is the etiology of immune thrombocytopenia?

A
  • may present 1-2 weeks after an immune trigger
    • viral illness
    • live virus immunization
    • allergic rxn
  • can be presenting symptom of broader immune disease (HIV, SLE)
  • can be brought on by specific infections - HepC and H. Pylori
  • lymphoid malignancy
23
Q

What is the pathophysiology of congenital TTP?

A
  • Gene that makes ADAMST13 is mutated, resulting in lowered production of the enzyme
24
Q

What is the pathophysiology of immune-mediated TTP?

A
  • B-cell mediated autoantibody production against von Willebrand cleaving protease (ADAMS13)
25
Q

How do you treat TTP?

A
  • early diagnosis crucial - DO NOT MISS
  • plasmapheresis is the main treatment
    • replaces ADAMST13 and reduces any antibody
    • in acute phase, 1.5 L
    • maintains congenital 3-4 weeks
  • steroids for immune-mediated TTP
  • Platelet transfusions contraindicated unelss bleeding is life-threatening
26
Q

What is the second-line treatment for TTP if plasmaphoresis fails?

A
  • Immune mediated:
    • splenectomy
    • corticosteriods
    • rituximab (MAb - 95% of case reports)
27
Q

What is secondary hemostasis (coagulative factor bleeding)?

A
  • bleeding from large vessels
  • subcutaneous hematomoas
  • hemarthroses - bleeding into joint spaces
  • intramuscular hematomas
28
Q

What is pseudothrombocytopenia?

A

Where platelet counts are artificially reduced on CBC/peripheral smears because the platelets have all aggregated into clumps (improper handling of sample).

29
Q

What is the epidemiology of ITP?

A
  • all genders, races and ages (used to be thought of as a young woman’s disease - not true)
  • 10-40 per 100k prevalence
30
Q

What are the categories of ITP?

A
  • Acute: within three months of diagnosis
  • persistent: 3-12 months from diagnosis (80% of ITP in childhood will spontaneously resolve in 6-12 months)
  • chronic ITP: lasting more than 12 months (80% of adult cases go on to be chronic)
31
Q

What is the pathophysiology of ITP?

A
  • loss of self-tolerance
  • autoantibodies (IgG) against platelet antigens
    • platelet gycoproteins (IIb/IIIa and Ib/IX)
    • cellular mechanisms
  • platelets get coated with autoantibodies
  • get destroyed (retiuloendothelial system) - bind to Fc receptros on macrophages, then get eaten
  • decreased production
32
Q

What is the key point to know about the pathophysiology of ITP?

A

Polyclonal autoantibodies may inhibit platelet production by inhibiting megakaryocyte maturation

33
Q

What is the clinical presentation of ITP?

A
  • bleeding
    • mucocutaneous bleeding
      • wet -oral bullae, epistaxis, menorrhagia, gingival and GI bleeding
      • dry - bruising and petechiae
34
Q

What does the CBC/PBS of ITP look like?

A
  • thrombocytopenia <100 x 109/L
  • normal platelet granulation
  • occasional large platelets
  • normal WBC # and diff
  • normal RBC # and appearance (unless active bleeding)
  • no evidence of hemolysis
35
Q

How do you diagnose ITP?

A
  • Diagnosis of exclusion
  • no splenomegaly, lymphadenopathy
  • other CBC indices normal
36
Q

ITP in adults - what additional tests should be done for new onset?

A
  • Test for HIV and HCV
  • broader immune dysfunction
    • DAT - prior to anti-D
    • quantiative immunoglobins
37
Q

What are the treatments for ITP?

A
  • IVIg
  • anti-D
  • corticosteroids
38
Q

What is IVIG treatment?

A
  • derived from human plasma
  • blocks Fc receptors on macrophages from binding with autoantibody coated platelets
  • adverse effects include nausea, vomiting, headache (also sx of head bleed), fever
    • aceptic meningitis (rare)
    • alloimmune hemolysis (rare)
    • infection transmission exceedingly rare
    • anaphylaxis in IgA deficient pt.
39
Q

What are the pros and cons of IVIG?

A

Pros

  • lack of long term side effects
  • efficacious in 1-2 doses (lasts 2-4 wks)

Cons

  • several hour IV infusion
  • very $$$
  • difficult side effects
  • derived from pooled human plasma
40
Q

What is Anti-D immunoglobin therapy?

A
  • polyclonal Ab derived from human Ig
  • Rh(D) antigen positive, non-splenectomized pts can receive
  • preferential destruction of antibody-coated RBCs, spares the platelets (sacrifices RBC)
  • adverse events: fever, chills, nausea, vomiting (give premedications)
41
Q

What are the pros and cons of Anti-D therapy?

A

Pros

  • short IV infusion
  • efficacious
  • fewer donors per dose than IVIG

Cons

  • side effect of hemolysis
  • really small chance <0.05% massive intravascular hemolysis
  • no no if baseline hemolysis (DAT/Coombs BEFORE starting therapy)
  • have to avoid in anemia, acute illness, abormal renal function, patients > 65
42
Q

What is the biggest risk to avoid in ITP?

A

Intracranial hemorrhage

  • rare <1%, but deadly
  • patients with lowest platelet counts at highest risk <20k
  • life-threatening spontaneous bleeding at very low counts
  • eliminate anti-platelet medications and high risk activity
43
Q

How is corticosteriod therapy used in treating ITP?

A
  • 1st line in adult ITP patients
  • masks leukemia, so you need to avoid as first line in children
  • predinose, methylprednisone, dexamethasone
  • less rapid platelet rise than in other therapies
  • get massive weight gain
44
Q

What are the urgent treatment options for ITP?

A
  • platelet infusions/drip
  • emergency splenectomy
  • IV methylprednismoe
  • IVIG
  • recombinant FVIIa (extrinsic pathway that will push toward clotting)
45
Q

What is the treatment for chronic ITP?

A
  • splenectomy
    • effective 75%
    • but many post-splenectomy complications
  • Rituximab (specifically against B cells)
  • thrombopoietin receptor agonists - binds to megakaryocytes and stimulates platelet production
  • Azathioprine - immunosuppressant
46
Q

ITP vs TTP - How do you tell them apart?

A

Patient Population:

Young child - suspect ITP over TTP (note congenital TTP)

Clinical Symptoms: ITP often has no symptoms other than mucocutaneous bleeding. NO splenomegaly and no hemolytic anemia or neuro symptoms.

Diagnosis: ITP is isolated thrombocytopenia, but TTP has hemolytic anemia, increased indirect bilirubin, decreased haptoglobin

Clin Med - Hematology (9 decks)

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