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Renal > Thrombotic Microangiopathies > Flashcards

Thrombotic Microangiopathies Flashcards

1
Q

What are the 3 shared features of all thrombotic microangiopathies (TMAs)?

A
  1. microangiopathic hemolytic anemia
  2. thrombocytopenia
  3. organ injury due to microthrombi
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2
Q

Define “renal restricted” thrombotic microangiopathy

A

when the only organ that is affected by microthrombi is the kidney

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3
Q

What is the first event in all forms of TMA?

A

Damage to the vascular endothelium is the initial event in all forms of TMA.

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4
Q

Why does hemolytic anemia occur in TMA?

A

Fragmented red blood cells (hemolytic anemia) occurs due to shear stress in microvasculature with thrombi.

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5
Q

Why does thrombocytopenia occur in TMA?

A

Thrombocytopenia occurs due to platelet consumption in thrombi.

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6
Q

Why is the glomerulus so susceptible to injury in TMAs? (4)

A
  1. fenestration
  2. high capillary pressure
  3. exposure to toxins and complement activation of high blood flow
  4. GBM is very pro thrombotic, and can be exposed when the endothelium dies
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7
Q

What are the 3 factors that can protect the glomerular microvascular bed in TMAs?

A
  1. VEGF
  2. complement regulatory proteins
  3. ADMTS13 - a VWF protease that limits platelet aggregation
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8
Q

What is ADAMTS13?

A

a VWF protease that breaks down VWF multimers to prevent platelet aggregation and therefore, thrombi. it is very low in some forms of TMA

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9
Q

What are the 3 main classes of TMA?

A
  1. thrombotic thrombocytopenic purpura
  2. hemolytic uremic syndrome
  3. “other”
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10
Q

What are the 2 main subtypes of hemolytic uremic syndrome, which is a TMA

A
  1. typical/diarrheal (D+HUS)

2. atypical complement mediated

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11
Q

What causes typical HUS?

A

shiga toxins, which cause diarrhea in E Coli infections as well as HUS

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12
Q

What causes atypical HUS?

A

abnormalities in complement regulation, without shiga toxin

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13
Q

What are the 2 main types of “other” TMAs?

A

anti-VEGF

endothelial damage due to other causes

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14
Q

Preeclampsia and HEELP syndrome are examples of what kind of TMA?

A

anti VEGF associated

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15
Q

Drugs such as bevaciumab, sutent and sorafenib can cause what kind of TMA?

A

anti-VEGF associated TMA

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16
Q

transplant rejection, HIV, cancer, drugs, connective tissue disease, malignant hypertension, antiphospholipid syndrome can all cause what kind of TMA?

A

endothelial damage associated TMA

17
Q

What is the presentation of thrombotic thrombocytopenic purpura? (5)

A

hemolytic anemia, thrombocytopenia, neurologic symptoms, kidney injury, fever

18
Q

hemolytic anemia, thrombocytopenia, neurologic symptoms, kidney injury, fever

This is a typical presentation for what disease?

A

thrombotic thrombocytopenia purpura

19
Q

What causes TTP?

A

-absence of ADAMTS13 activity (due to genetic mutation in ADAMTS13 gene OR autoantibodies to ADAMTS13) leads to large multimers of von Willebrand Factor (VWF) that increase platelet aggregation and thrombus formation

20
Q

How is TTP treated?

A

plasmapheresis and exchange (remove the antibody and/or give back the enzyme)

21
Q

What strain of E coli causes HUS?

A

O157

22
Q

Who is most commonly affected by D+HUS?

A

children, due to E Coli infection

23
Q

What pathophysiology is responsible for D+HUS?

A

Gb3 receptor on glomerular endothelial cells causes platelet thrombi when shiga toxin binds

24
Q

When is D+HUS treated with drugs?

A

with severe neurological involvement

25
Q

How is D+ HUS treated?

A

supportive, plasmapheresis and Eculizimab (see treatment for atypical HUS below) have been tried in patients with severe neurologic involvement

26
Q

Which type of HUS has worse outcomes: D+HUS or atypical?

A

atypical

27
Q

What is the most common defect that is observed in atypical HUS?

A

mutations in the gene encoding Factor H or autoantibodies to Factor H are the most common defects observed

28
Q

How is atypical HUS treated?

A

plasmapheresis and exchange to remove the autoantibody and/or give back normal Factor H to deficient patient were standard

New therapy: monoclonal C5a antibody

29
Q

This disease in pregnant women is characterized by TMA, hypertension, thrombotic microangiopathy in kidney, neurologic features (hyperreflexia – may progress to seizures and eclampsia) hemolytic anemia (fragments on smear) and thrombocytopenia. What causes it?

A

Placental defect

30
Q

When does preeclampsia generally occur?

A

after the 20th week of pregnancy

31
Q

What are the risk factors for preeclampsia?

A

first pregnancy
twins
molar pregnancies

32
Q

What is the pathophysiology of preeclampsia?

A

circulating VEGF receptor is released by the placenta with inappropriate spiral artery formation. This sucks up the VEGF in the body, leading to HTN and damage to the glomerular endothelium

33
Q

What is the treatment for preeclampsia?

A

deliver the baby, MgSO4 for neurologic symptoms, blood pressure control (detailed treatment will be discussed in OB/GYN)

34
Q

patients with this disease will have hypertension, kidney injury with glomerular endotheliosis (swollen endothelial cells), platelet-rich thrombi

A

Anti-VEGF drug induced TMA

35
Q

How do you treat anti-VEGF drug induced TMA?

A

drug holiday (stop the drug), if systemic features with low platelets and hemolytic anemia, plasmapheresis has been tried

36
Q

A 40 y.o. female presents to the emergency room with numbness in her right arm and a headache. Routine CBC shows anemia and platelets of 60,000. An MRI is performed, which shows no abnormalities. Which of the following findings helps to confirm diagnosis of a TMA? A) white blood cell differential
B) blood smear showing RBC fragments (shistocytes)
C) blood chemistry showing abnormal liver function tests
D) high ADAMTS13 enzymatic activity

A

B - blood smear showing RBC fragments (shistocytes)

37
Q

A 40 y.o. female presents to the emergency room with numbness in her right arm and a headache. Routine CBC shows anemia and platelets of 60,000. An MRI is performed, which shows no abnormalities. Her CBC shows 15% fragmented red blood cells. In the ER, her symptoms resolve. The most appropriate treatment is: a) follow-up with hematology as an outpatient b) admission for platelet and red blood cell transfusion c) admission to hospital for plasmapheresis and plasma exchange

A

c) admission to hospital for plasmapheresis and plasma exchange

Renal (28 decks)

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