128 Thrombotic Microangiopathies

Question 1

Refers to thrombotic microangiopathy without another apparent cause and without acute renal injury at presentation, although mild or modest renal insufficiency may be seen.

Answer 1

Thrombotic thrombocytopenic purpura (TTP)

Question 2

TTP is associated with autoantibodies against the plasma metalloprotease ____________ that reduce plasma activity to less than 10% of normal.

Answer 2

ADAMTS13

Question 3

TRUE OR FALSE

TTP is caused by unregulated VWF-dependent platelet thrombosis.

Answer 3

TRUE

TTP is caused by unregulated VWF-dependent platelet thrombosis.

Question 4

ADAMTS13 deficiency in TTP is caused by polyclonal autoantibodies against ADAMTS13, usually immunoglobulin ____

Answer 4

(Ig) G

Occasionally IgA or IgM

These antibodies almost always bind the ADAMTS13 spacer domain, and often bind to the CUB domains and first thrombospondin-1 repeat; they bind less frequently to other thrombospondin-1 repeats, the metalloprotease domain, or the propeptide

Question 5

TRUE OR FALSE

Autoantibodies associated with increased ADAMTS13 clearance are related to reduced mortality and refractory disease.

Answer 5

FALSE

Autoantibodies associated with increased ADAMTS13 clearance are related to increased mortality and refractory disease.

Question 6

TRUE OR FALSE

The demographics of TTP are similar to those of systemic lupus erythematosus (SLE).

Answer 6

TRUE

The demographics of TTP are similar to those of systemic lupus erythematosus (SLE).

• TTP is relatively uncommon before age 20 years, with a peak incidence between ages 30 and 50 years.
• Across many reports, the female-to-male ratio averages approximately 2:1, but female preponderance is more pronounced below age 50 years, and the ratio approaches equality above age 60 years.
• Other risk factors for TTP include African ancestry and obesity.
• HLA-DRB1*11 is overrepresented severalfold in whites with TTP.

Question 7

Approximately_____ of patients have symptoms of hemolytic anemia.

Answer 7

One-third

Anemia is almost universal, with a mean hemoglobin of approximately 80 g/L.
Thrombocytopenia typically is severe, with a mean platelet count of approximately 20 x109/L.

Question 8

Systemic microvascular thrombosis typically affects the kidney, heart, brain, pancreas, adrenals, skin, spleen, marrow, and most other tissues except the ______, which are spared.

Answer 8

Lungs & liver

Question 9

TRUE OR FALSE

Renal involvement is common, but acute renal failure occurs in fewer than 30% of cases.

Answer 9

FALSE

Renal involvement is common, but acute renal failure occurs in fewer than 10% of cases.

Question 10

Macrovascular venous or arterial thrombosis occurs in up to__________of patients

Answer 10

One-half

Question 11

Approximately _____ of patients have a positive antinuclear antibody test.

Answer 11

50%

The symptoms and signs of TTP are nonspecific.
In most cases of acute TTP, there is no obvious predisposing cause.

Question 12

The characteristic morphologic feature of TTP on the blood film

Answer 12

Marked increase in schistocytes

Schistocytes are helmet cells, or small irregular triangular or crescent-shaped cells with pointed projections, that lack central pallor

Schistocytes occur in a variety of conditions besides TTP, although the level seldom enters the 1% to 18% range typical of TTP.

Question 13

ADAMTS13 activity is characteristically less than ________ and this degree of ADAMTS13 deficiency appears to be specific for TTP.

Answer 13

10% or 10 IU/dL

Question 14

Other conditions with decreased ADAMTS13 levels

Answer 14

Newborns, during pregnancy, after surgery, and in chronic liver cirrhosis, chronic renal insufficiency, stroke, coronary disease, acute inflammatory states

Question 15

Inherited ADAMTS13 deficiency, with mutations in ADAMTS13

Answer 15

Upshaw-Schulman Syndrome or Congenital Thrombotic Thrombocytopenic Purpura

Question 16

The mainstay of therapy for TTP

Answer 16

Plasma exchange

Aiming to replenish adequate ADAMTS13
Should be started as soon as is feasible

Question 17

The optimal dose of plasma is not known, but a common practice is to perform plasma exchange ________________

Answer 17

Once daily at a volume of 40 or 60 mL/kg, equivalent to 1.0- or 1.5-times plasma volumes

For refractory disease, the intensity of plasma exchange can be increased to twice daily.

Question 18

Prompt treatment is important, and if plasma exchange must be delayed more than a few hours,_________ infusion should be given by simple infusion at _________mL/kg total dose per day, consistent with the patient’s ability to tolerate the fluid load.

Answer 18

Plasma
10–20 mL/kg

High-dose glucocorticoid, such as methylprednisolone, can also be given if there is a delay.

Question 19

TRUE OR FALSE

Cryosupernatant is depleted in the largest VWF multimers but has normal ADAMTS13 levels, which could make cryosupernatant particularly suitable for the treatment of TTP.

Answer 19

TRUE

Cryosupernatant is depleted in the largest VWF multimers but has normal ADAMTS13 levels, which could make cryosupernatant particularly suitable for the treatment of TTP.

Nevertheless, small randomized trials suggest that cryosupernatant is not superior to fresh-frozen plasma for the initial treatment of TTP.

Question 20

Plasma exchange should be continued daily until the patient has a treatment response as shown by a platelet count greater than __________X 109/L for at least _______ days.

Answer 20

Greater than 150 X 109/L

At least 2 days

Question 21

Glucocorticoid options for TTP

Answer 21

Prednisone 1 mg/kg orally, in one or two doses, for the duration of plasma exchange, followed by tapering

Methylprednisolone 1 g intravenously daily for 3 days

High-dose methylprednisolone (10 mg/kg/d for 3 days followed by 2.5 mg/kg/d) was more effective than standard-dose methylprednisolone (1 mg/kg/d) in a small randomized trial

Question 22

Low-dose aspirin (eg, 80 mg/d orally) has been suggested for thromboprophylaxis, once the platelet count exceeds _______ x 109/L.

Answer 22

50 x 109/L

Question 23

TRUE OR FALSE

Platelet transfusions are given outright in TTP for the treatment of life-threatening hemorrhage, preferably after plasma exchange treatment has been initiated.

Answer 23

FALSE

Platelet transfusions are relatively contraindicated and should be reserved for the treatment of life-threatening hemorrhage, preferably after plasma exchange treatment has been initiated.

Transfusion of platelets may correlate with acute deterioration and death in TTP.

Question 24

Therapy for TTP that is refractory to plasma exchange

Answer 24

Rituximab (eg, 375 mg/m2 intravenously weekly for 4 doses)

Should be administered immediately after plasma exchange to maximize the interval until the next plasma exchange.

Question 25

TRUE OR FALSE

Splenectomy can result in lasting remissions or reduce the frequency of relapses for some patients with TTP that is refractory to plasma exchange or immunosuppressive therapy, presumably by removing a major site of anti-ADAMTS13 antibody production.

Answer 25

TRUE

Splenectomy can result in lasting remissions or reduce the frequency of relapses for some patients with TTP that is refractory to plasma exchange or immunosuppressive therapy, presumably by removing a major site of anti-ADAMTS13 antibody production.

Question 26

Other treatments for TTP

Answer 26

Vincristine : 2 mg intravenously on day 1 followed by 1 mg on days 4 and 7, or 2 mg intravenously per week for 2 to 14 weeks

Oral cyclosporine 2 to 3 mg/kg daily in two divided doses as an adjunct to plasma exchange

Oral or IV cyclophosphamide; oral azathioprine; bortezomib, mycophenolate,100 N-acetylcysteine, combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone, and autologous stem cell transplantation

Question 27

An anti-VWF dimeric nanobody, binding to the GP1b receptor on VWF licensed for the treatment of acute TTP

Answer 27

Caplacuzimab

Question 28

Trials of Caplacuzimab

Answer 28

TITAN106 and HERCULES

Question 29

Caplacuzimab causes severe VWF activity deficiency, the bleeding risk is typically mild to moderate, with __________ symptoms most common

Answer 29

Epithelia-based symptoms most common, such as epistaxis and gingival bleeding

The greatest risk to patients who initiate therapy for TTP is between 7 and 10 days.

Caplacuzimab acts as an adjunctive therapy to normalize platelets and prevent further microvascular damage, but it has no impact on the underlying pathology, in relation to ADAMTS13.

Question 30

A commonly used protocol for the treatment of acute TTP, once confirmed by severe deficiency of ADAMTS13 (<10 IU/dL)

Answer 30

Plasma exchange, caplacuzimab, and immunosuppression (in particular, steroids and rituximab)

Question 31

Frequency of laboratory monitoring: complete blood count with platelet count, LDH, electrolytes, blood urea nitrogen, and creatinine

Answer 31

Daily

Question 32

Prophylaxis for venous thromboembolism may be instituted with low-molecular-weight heparin and low-dose aspirin can be started once platelt count

Answer 32

Above 50 x 109/L

Question 33

Exacerbations in TTP are defined as

Answer 33

TTP recurring within 30 days after a treatment response

25% to 50% of patients have an acute exacerbation within 2 weeks that requires further treatment with plasma exchange

Question 34

Relapses in TTP is defined as

Answer 34

Recurrences more than 30 days after a complete response

Occur in up to one-third of patients within 2 years after treatment with plasma exchange and glucocorticoids alone

There may be an associated trigger, such as infection, surgery, or pregnancy.

Relapses in TTP are associated with severe ADAMTS13 deficiency and detectable ADAMTS13 autoantibody inhibitors.

Question 35

The mortality rate for TTP treated with plasma exchange ranges from ______%

Answer 35

10% to 20%

Most deaths occur within a few days after presentation, and almost all occur within the first month.

However, the early use of caplacuzimab will reduce the mortality rate acutely, when initiated as soon as a diagnosis of acute TTP is confirmed.

Question 36

Other name for Congenital TTP

Answer 36

Upshaw-Schulman syndrome

Question 37

Congenital TTP, or Upshaw-Schulman syndrome is autosomal ___________ and affects the genders almost equally

Answer 37

Autosomal recessive

Question 38

Clinical features of Congenital TTP, or Upshaw-Schulman syndrome

Answer 38

Neonatal jaundice and hemolysis but no evidence of ABO blood group or Rh incompatibility

Severe congenital ADAMTS13 deficiency (<5%)

Question 39

TRUE OR FALSE

Females often present during their second pregnancy, possibly because VWF levels are decreased late in pregnancy.

Answer 39

FALSE

Females often present during their first pregnancy, possibly because VWF levels are increased late in pregnancy.

TTP usually occurs in the third trimester or postpartum, whereas fetal loss is most common in the second trimester

Question 40

Treatment for congenital TTP

Answer 40

Periodic infusions of fresh-frozen plasma or an equivalent virucidally treated product

The half-life of ADAMTS13 is 2 to 3 days; 5 to 20 mL/kg of plasma every 2 to 3 weeks was considered sufficient to maintain ADAMTS13 at a greater than 5% level and prevent symptoms.

Furthermore, the maximum ADAMTS13 activity levels achieved with approximately 10 to 15 mL/kg of plasma infused is 30 IU/dL.

In contrast, with use of recombinant ADAMTS13, ADAMTS13 activity levels of 100 IU/dL are measured.

Question 41

Given to patients with severe allergic reactions to plasma

Answer 41

Plasma-derived factor VIII/VWF concentrates

However, ADAMTS13 activity levels are not measurable in these products.

Question 42

TRUE OR FALSE

ADAMTS13 replacement therapy is required throughout pregnancy and the postpartum period

Answer 42

TRUE

ADAMTS13 replacement therapy is required throughout pregnancy and the postpartum period

Fetal loss and premature birth can be prevented by plasma infusions of 10 mL/kg every 2 weeks beginning at 8 weeks of gestation, increasing to weekly in the second trimester.

Question 43

Patients with ADAMTS13 activity of less than ____ % of normal tend to have their first TTP episode in childhood, have more than one episode of TTP per year, and require regular plasma prophylaxis.

Answer 43

Less than 2.5%

Question 44

Refers to thrombotic microangiopathy that mainly affects the kidney and usually causes oliguric or anuric renal failure

Answer 44

Hemolytic uremic syndrome

Diarrhea-associated HUS and “typical” HUS

Question 45

TRUE OR FALSE

HUS was often preceded by a diarrheal illness and, unlike TTP in adults, the prognosis was relatively favorable.

Answer 45

TRUE

HUS was often preceded by a diarrheal illness and, unlike TTP in adults, the prognosis was relatively favorable.

Question 46

Two types of Shiga toxin (Stx)

Answer 46

• Stx1: identical to Shigella dysenteriae serotype 1 toxin
• Stx2 is approximately 50% identical in sequence to Stx1 and occurs in several closely related forms.

Both toxins consist of pentameric B subunits that bind globotriaosylceramide (Gb3) on cell surfaces and a single A subunit that is responsible for cytotoxicity.

The observed predilection for renal injury is a result of the relatively high expression of Gb3 on renal tubular epithelial, mesangial, and glomerular endothelial cells.

Question 47

Accounts for at least 80% of cases of STEC-HUS

Answer 47

E coli O157:H7

Question 48

Percentage of patients with bloody diarrhea and E coli O157:H7 infection that will develop STEC-HUS

Answer 48

15%

The acute onset of microangiopathic hemolytic anemia, thrombocytopenia, and renal injury an average of seven days (range, 5–13) after the onset of diarrhea.

Question 49

STEC-HUS mainly affects what area of the kidney

Answer 49

Renal cortex

Often shows extensive necrosis

Question 50

TRUE OR FALSE

Antibiotics should not be used early in the course of acute diarrheal illness caused by E. coli O157:H7 because antibiotics increase the risk of HUS.

Answer 50

TRUE

Antibiotics should not be used early in the course of acute diarrheal illness caused by E. coli O157:H7 because antibiotics increase the risk of HUS.

Antimotility agents and narcotics increase the risk of HUS and neurologic complications.

Nonsteroidal antiinflammatory drugs and antihypertensives that reduce renal perfusion such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers should be avoided.

Question 51

Signals the end of the period of risk for developing HUS

Answer 51

A rising platelet count

Question 52

HUS not associated with Stx-producing organisms

Answer 52

Diarrhea-negative HUS or aHUS

Question 53

Mutation that cause of familial HUS

Answer 53

Complement factor H (CFH)

These results provided a rationale for treating aHUS with inhibitors of complement activation, which has proved very effective

Question 54

Drives the pathogenesis of aHUS

Answer 54

Alternative complement pathway

Complement component C3 is spontaneously converted to C3b at a low rate and deposited on cell surfaces.

Under normal circumstances, this C3b is promptly cleaved and inactivated by the serine protease factor I, and this reaction is accelerated by factor H or membrane cofactor protein (MCP, CD46).

Question 55

TRUE OR FALSE

Approximately 60% of affected children with aHUS have their first episode of aHUS before age 2 years, and 25% before age 6 months.

Answer 55

TRUE

Approximately 60% of affected children with aHUS have their first episode of aHUS before age 2 years, and 25% before age 6 months.

In contrast, STEC-HUS is rare before age 6 months.

Question 56

TRUE OR FALSE

Childhood aHUS affects males and females equally, whereas onset in adults disproportionately affects females mainly because of disease triggered by pregnancy.

Answer 56

TRUE

Childhood aHUS affects males and females equally, whereas onset in adults disproportionately affects females mainly because of disease triggered by pregnancy.

Question 57

Clinical features of aHUS

Answer 57

• Present acutely with thrombotic microangiopathy and renal failure, sometimes with progressive hypertension
• Not classically preceded by bloody or painful diarrhea
• Women with pregnancy-associated aHUS usually present postpartum

Question 58

Most common extrarenal symptom of aHUS

Answer 58

CNS

Question 59

Treatment for aHUS

Answer 59

Plasma Exchange
Eculizumab

After excluding severe ADAMTS13 deficiency, STEC, and secondary causes of thrombotic microangiopathy, plasma exchange can be stopped and eculizumab started for presumptive aHUS

Question 60

Dosing of Eculizumab

Answer 60

900 mg intravenously every week for four weeks, followed by 1200 mg in week 5 and every other week thereafter

Supplementary doses are recommended during plasma exchange or infusion,but concurrent plasma exchange and eculizumab are not beneficial and should be avoided.

Question 61

The most significant risk in patients receiving eculuzimab

Answer 61

Meningitis infection

Therefore, patients need to receive the tetravalent and serotype type B meningitis vaccines.

Children also should be vaccinated for S. pneumoniae and Haemophilus influenzae type b.

Concomitant antibiotic prophylaxis is also recommended throughout the period of eculizumab therapy

Question 62

Can be added to eculizumab for treatment of aHUS caused by autoantibodies to CFH

Answer 62

Rituximab and glucocorticoids

If the autoantibodies are eradicated, then eculizumab can be discontinued.

Question 63

TRUE OR FALSE

In renal transplantation in aHUS, living related donors generally are used.

Answer 63

FALSE

In renal transplantation in aHUS, living related donors generally are not used.

Mutation screening should be performed before transplantation to guide subsequent therapy.

HUS has not recurred after renal transplantation in children with DGKE mutations.

Question 64

Mutation that is associated with a less aggressive clinical course: patients may improve during plasma exchange but have similar outcomes without plasma exchange, with 90% alive and free of dialysis after several years

Answer 64

MCP mutations

Question 65

Mutation that is associated with the development of nephrotic syndrome, which is otherwise uncommon in aHUS.

Answer 65

DGKE mutations

Question 66

Causes of secondary thrombotic microangiopathy

Answer 66

Metastatic cancer, malignant hypertension, systemic infection, solid-organ or hematopoietic stem cell transplantation, vasculitis, catastrophic APS, radiation exposure, chemotherapy, certain other drugs, inherited or acquired metabolic disorders, and various causes of disseminated intravascular coagulation

Endothelial injury may be a common cause, although the mechanism of disease varies and in most cases is not understood.

Question 67

TRUE OR FALSE

Severe ADAMTS13 deficiency almost never occurs in secondary thrombotic microangiopathy, and treatment with plasma exchange, rituximab, or eculizumab is not known to be beneficial.

Answer 67

TRUE

Severe ADAMTS13 deficiency almost never occurs in secondary thrombotic microangiopathy, and treatment with plasma exchange, rituximab, or eculizumab is not known to be beneficial.

Question 68

Thrombotic microangiopathy, often with acute renal failure, is a rare complication of invasive infections with _____________ in children.

Answer 68

S. pneumoniae

The pathophysiology is thought to involve bacterial neuraminidase, made by S pneumoniae and some other organisms, which removes sialic acid residues from cell surface glycoproteins and exposes Thomsen-Friedenreich antigen (T antigen).

Question 69

Recipients of solid-organ transplants can develop thrombotic microangiopathy, often dominated by renal involvement associated with immunosuppression by _______________

Answer 69

Cyclosporine or tacrolimus

ADAMTS13 levels are normal,and plasma therapy is ineffective.

Question 70

Cancer-associated paraneoplastic hypercoagulability and thrombosis

Answer 70

Trousseau syndrome

Thrombotic microangiopathy occurs in a small fraction of patients with cancer, most commonly with adenocarcinoma of the pancreas, lung, prostate, stomach, colon, ovary, breast, or unknown primary site that usually is widely metastatic.

Plasma exchange is ineffective.

Question 71

TRUE OR FALSE

The thrombosis of Trousseau syndrome may respond to anticoagulation with warfarin but not heparin

Answer 71

FALSE

The thrombosis of Trousseau syndrome may respond to anticoagulation with heparin but not warfarin

Question 72

Leukemia associated with abundant schistocytes

Answer 72

Acute erythroleukemia

Question 73

Differential diagnosis of thrombotic microangiopathy in pregnancy

Answer 73

Preeclampsia, eclampsia, HELLP syndrome (hemolysis, elevated liver enzymes, low platelet count), acute fatty liver of pregnancy, abruptio placentae, amniotic fluid embolism, and retained products of conception

Pregnancy also can trigger disease in patients with congenital or acquired ADAMTS13 deficiency or defects in the alternative complement pathwa

Question 74

How to distinguish Evan syndrome from TTP

Answer 74

Positive Coombs test and the prominence of spherocytes relative to schistocytes in the blood film

Question 75

Example of drugs that cause drug-induced thrombotic microangiopathy

Answer 75

Quinine*
Cyclosporine and tacrolimus
Ticlopidine*
Emicizumab
Mitomycin C
Gemcitabine
Sunitinib and bevacizumab

Some agents cause disease by an immune (*) mechanism and others by direct toxicity; a few drugs reportedly act by either mechanism.

In all these therapies, the thrombotic microangiopathy is idiosyncratic and often preceded by hypertension, before development of a TMA with primarily renal involvement.

Question 76

The most common cause of drug-induced thrombotic microangiopathy

Answer 76

Quinine

Question 77

Antiplatelet drug that induces autoantibody inhibitors of ADAMTS13, effectively causing TTP that responds to plasma exchange.

Answer 77

Ticlopidine

The related thienopyridine drugs clopidogrel, prasugrel, and ticagrelor do not appear to cause thrombotic microangiopathy by this mechanism.

Plasma exchange appears to be ineffective or possibly harmful for other drug-induced thrombotic microangiopathy

Question 78

A rare autosomal recessive condition caused by mutations in the MMACHC (methylmalonic aciduria and homocystinuria type C protein) gene

Answer 78

Cobalamin C deficiency

Treatment with high-dose hydroxocobalamin and betaine may reverse or prevent HUS.