Hemolytic Anemia Flashcards
hemolytic anemia occurs when ____ exceeds ____
common features?
rate of hemolysis exceeds rate of bone marrow RBC production
could be due to acute blood loss (would see symptoms/signs of low blood volume) or hemolysis
common features: HIGH reticulocytes (3x or more), shortened RBC lifespan, elevated EPO and erythropoiesis, clinical/laboratory evidence of RBC destruction
how can the high reticulocyte count seen in hemolytic anemia affect MCV?
reticulocytes are a bit larger than mature RBC (also are bluish and lack central pallor)
increase mean corpuscular volume (MCV)
splenic macrophages remove old/damaged RBC as they pass from ____ and _____
cords to sinusoids
changes in RBC surface proteins with age allow macrophages to bind
old RBC are also less flexible to fit through endothelial slits (spleen is like a filter)
unconjugated bilirubin from broken down RBC in spleen is very hydrophobic and toxic, so it circulates in plasma bound to ____
albumin, which takes it to liver for excretion (to bile, where it becomes conjugated to be water soluble)
[remember that RBC breakdown also releases iron, which is recycled]
hemolysis occurs when either 2 things occurs:
- extravascular: increased number of RBC are trapped in the spleen (cannot get through filter - endothelial slits) —> splenomegaly and increase in red pulp
- intravascular: RBC lyse within blood vessels
in hemolytic anemia due to increased number of RBC getting trapped in the spleen, what happens to the spleen and the liver?
splenomegaly and increased red pulp relative to white pulp
high amount of unconjugated bilirubin being taken to liver (carried by albumin) overwhelms liver, so there is an increase in unconjugated bilirubin in the blood, and increased conjugated bilirubin seen in the bile and intestine
increased unconjugated bilirubin in blood —> jaundice
in hemolytic anemia due to an increased number of RBC trapped in the spleen, there is an increase in unconjugated bilirubin (bound by albumin) in the blood. what clinical feature does this cause?
jaundice (icterus) - due to deposition of bilirubin in tissues (hyperbilirubinemia)
most noticiable in sclerae (eyes) - have high affinity for bilirubin
(total change in bilirubin must be at least 3mg/dL to detect a change)
in hemolytic anemia due to increased RBC being trapped in spleen, there is an increase in both unconjugated bilirubin (in the blood) and conjugated bilirubin (in bile and intestine). What do each of these cause
high unconjugated bilirubin in blood - causes jaundice (deposited in tissues)
high conjugated bilirubin in bile and intestines - causes gallstones
why is lactate dehydrogenase an important hemolytic marker?
lactate dehydrogenase - enzyme in anaerobic glycolysis (which is how RBC make ATP)
can leak out when RBC are broken down in spleen
*note that this enzyme is nonspecific for RBC, but very abundant in RBC
why is free hemoglobin toxic? what molecule in the body binds free hemoglobin and gets rid of it?
heme can be released from globin - consumes nitric oxide (NO) and causes oxidative damage to cells
haptoglobin (produced by liver) has high affinity for free hemoglobin and binds irreversibly —> confines hemoglobin to plasma and prevents heme release
*note that this consumes haptoglobin because binding is irreversible, so in splenic hemolysis, there will be a decrease in serum haptoglobin
when hemolysis is occurring in the spleen (lots of RBC getting trapped), describe how each of these are affected:
a. spleen size
b. unconjugated bilirubin
c. conjugated bilirubin
d. lactate dehydrogenase
e. serum haptoglobin
explain for each
a. spleen size: splenomegaly and more red pulp
b. unconjugated bilirubin: HIGH —> scleral icterus (jaundice)
c. conjugated bilirubin: HIGH (in bile and intestines)
d. lactate dehydrogenase: HIGH (abundant in RBC for anaerobic glycolysis)
e. serum haptoglobin: LOW (gets consumed from binding so much free hemoglobin)
when there are very high levels of lactate dehydrogenase and free hemoglobin in the blood, where is hemolysis likely occurring?
what protective protein will this deplete?
intravascularly
free hemoglobin (toxic) will exceed available haptoglobin (which binds free hemoglobin irreversibly) —> very low or absent haptoglobin and free hemoglobin in blood and urine
[remember that free hemoglobin causes oxidative damage and consumes nitric oxide —> vasoconstriction]
a patient with intravascular hemolysis complains of back/flank pain and dark urine - what is causing this?
free hemoglobin - directly toxic to tubules (causing kidney pain) and consumes NO (causing vasoconstriction)
hemoglobin levels exceed available haptoglobin
*plasma can appear red/pink, urine can appear brown/red, urine dipstick will test + for blood
chronic intravascular hemolysis can lead to renal _____
explain why
intravascular hemolysis —> renal hemosiderin
this occurs because free hemoglobin (very high in intravascular hemolysis) is toxic to renal tubules
will present with back/flank pain and brown/red urine
in intravascular hemolysis, describe how each of these is affected:
a. spleen size
b. unconjugated bilirubin
c. lactate dehydrogenase
d. serum haptoglobin
e. hemoglobinuria
f. hemosiderin
a. spleen size: normal
b. unconjugated bilirubin: HIGH —> scleral icterus (jaundice)
c. lactate dehydrogenase: VERY HIGH!
d. serum haptoglobin: VERY LOW
e. hemoglobinuria: HIGH
f. hemosiderin: HIGH (renal)
if hemolytic anemia is intrinsic to RBC, most cases are ____
if hemolytic anemia is extrinsic to RBC, most cases are ____
intrinsic to RBC - likely inherited (defect in RBC)
extrinsic to RBC - likely acquired
what are 3 general issues with RBC that could cause intrinsic/inherited hemolytic anemia?
issue with:
1. RBC membrane structure
2. enzyme function
3. hemoglobin structure
hereditary spherocytosis - cause, outcome
AD inheritance, mutation in spectrin, ankyrin, or Band 3 cytoskeletal proteins (causing loss of protein)
RBC lifespan reduced from 120d to 20d
spherocytes: small cells, lack central pallor, trapped in spleen, high concentration of hemoglobin within RBC (mean corpuscular hemoglobin concentration/ MCHC)
causes inherited/intrinsic hemolytic anemia
an increase in what is indicative of the presence of spherocytes?
increased MCHC: mean corpuscular hemoglobin concentration (avg hgb concentration per RBC)
(spherocytes are small due to membrane loss but contents are not changed)
spherocytes are less flexible and get trapped in spleen —> extravascular hemolysis (phagocytosed)
what specific type of anemia does this likely indicate:
- anemia with high reticulocyte count
- jaundice due to high unconjugated bilirubin
- splenomegaly due to RBC trapping
- pigment gallstones due to high conjugated bilirubin in bile
- increased MCHC
- negative direct Coomb’s test
hereditary spherocytosis: AD mutation in spectrin/ankyrin/Band3, causes extravascular (in the spleen) hemolytic anemia
*note that you must exclude autoimmune hemolytic anemia, which can also cause spherocytosis (via direct Coomb’s test)
if you’re considering hereditary spherocytosis for a patient, what must you exclude, and what test will you use?
hereditary spherocytosis: AD mutation in spectrin/ankyrin/Band 3 that causes extravascular hemolytic anemia
must exclude autoimmune hemolytic anemia with direct Coomb’s test (detects antibodies or complement bound to RBC), as this can also cause spherocytosis
what are 2 confirmatory tests for hereditary spherocytosis, which is an intrinsic extravascular hemolytic anemia?
- osmotic fragility test (old method): spherocytes can’t handle as much water (lower osmolarity)
[*note that thalassemia would have opposite result - more surface area, so can handle more water] - eosin-50maleimide flow cytometry (new method): binds RBC membrane protein Band 3 —> low in spherocytes
hereditary spherocytosis can be treated with _____ to correct chronic hemolysis
what will be seen in peripheral smear after?
treat with splenectomy —> Howell-Jolly bodies can be detected in peripheral smear following (RBC have a dark dot in them - remnants of nuclei that are usually removed by spleen)
glucose-6-phosphate dehydrogenase deficiency results in….
glucose-6-dehydrogenase is needed in hexose monophosphate shunt to produce NADPH, which produces glutathione (antioxidant, protects cells from oxidative damage)
G-6-PD deficiency: XLR trait (males higher risk), prevalent in patients with ancestors from areas where malaria is endemic —> protein misfolding and premature RBC destruction
Glucose-6-dehydrogenase deficiency produces what kind of anemia?
decrease G6PD —> decrease NADPH (via HMP, hexose monophosphate pathway) —> decrease glutathione —> more ROS
——> episodic hemolytic anemia, both intra- and extra- vascular
Heinz bodies and bite cells visible (hemoglobin precipitates)
what are the clinical features of G-6-PD deficiency?
triggering event causes oxidant exposure (food, drugs, infection)
oxidant leads to Hgb precipitation —> hemolysis 2-3 days later —> jaundice, anemia, dark urine, maybe back pain (kindeys)
increased LDH, decreased haptoglobin, increased unconjugated bilirubin, hemoglobinuria
bite cells and Heinz bodies seen
episodes are self-limited
what test is used to diagnose glucose-6-phosphate dehydrogenase deficiency?
fluorescent spot screening test: directly measures G6PD levels, must test after acute hemolytic episode
no fluorescent = no enzyme
describe glutathione redactase deficiency and its relation to anemia
glutathione reductase needed to produce glutathione (protection from ROS)
deficiency results in hemolysis —> hemolytic anemia
Heinz bodies and bite cells visible
describe pyruvate kinase deficiency and its relationship to anemia
pyruvate kinase needed for ATP production in RBC
deficiency: AR inheritance, cells with altered membranes (Burr cells) cleared by spleen —> hemolytic anemia
presents with:
- splenomegaly
- normcotyic anemia with high reticulocytes
- evidence of hemolysis
- Burr cells in peripheral smear
- negative Coomb’s test
[Burr cells have spicules around the cell membrane, look like little suns]
sickle cell disease is what kind of anemia? what/where is the mutation?
intrinsic/ inherited hemolytic anemia,
due to altered hemoglobin structure - missense mutation:
Glu—>Val in beta globin (HbS)
autosomal recessive, protective against malaria
what are risk factors for symptoms of sickling for patients with sickle cell trait (HbAS, heterozygous)? (3)
- dehydration
- high altitude (low oxygen pressure) - deoxygenated HbS polymerizes (“sticky”)
- infection
what 2 major problems do sickled cells cause clinically?
- chronic hemolytic anemia: mostly due to extravascular hemolysis (some intravascular though)
- microvascular occlusion: causes tissue ischemia
when does sickle cell disease present and what would you see on electrophoresis?
presents AFTER birth because at birth HbF is still majority - can start as soon as 6 months (when transition to HbA is supposed to happen, but HbS is present instead)
electrophoresis will show HbS, NO HbA (sickle cell trait would show HbS and HbA)
what can occur with severe untreated sickle cell anemia?
overproduction of EPO —> bone marrow expansion and skeletal deformities
maxillary bone hyperplasia, frontal bossing, delayed growth, fragile/brittle long bones, protruding teeth, “hair on end” skull x-ray
Patients with chronic hemolysis, particularly due to sickle cell disease, are at risk of infection from this virus. What is this virus, and what might infection from it result in for these patients?
parvovirus B19 - cytotoxic to RBC precursors and can transiently halt RBC production
can lead to aplastic crisis: abrupt, precipitous decline in hemoglobin occurring in patients with chronic hemolytic anemia
[remember that patients with chronic hemolysis require high RBC production to maintain oxygen levels]
contrast transient aplastic crisis with acute splenic sequestration
include in this comparison what parameters change and how
transient aplastic crisis: abrupt decline in hemoglobin, caused by parvovirus B19 which transiently stops RBC production
—> acute low Hgb, LOW reticulocytes, normal or high platelets
splenic sequestration crisis: sickle cells get captured and pool in spleen
—> acute low Hgb, abrupt splenomegaly, increased reticulocytes, decreased platelets
describe cause and symptoms of acute vaso-occlusive pain (sickle cell crises)
due to microvascular occlusion —> tissue ischemia
occurs as early as 6mo, lasts throughout life, triggered by infection/stress/dehydration/menses (sporadic, unpredictable)
acute severe pain located wherever the occlusion is
gold standard of diagnosis is patient’s report of pain and history of past episodes
“hand-foot syndrome” is also known as _____ and is caused by….
dactylitis: vaso-occlusion in the small bones of hands and feet cause bone infarction —> painful swelling and inflammation
skeletal complication of microvascular occlusion in sickle cell disease
can cause avascular necrosis of bone and makes bone susceptible to infection (osteomyelitis, esp. by salmonella)
in patients with sickle cell disease suffering from dactylitis, what type of infections are their bones susceptible to?
dactylitis: skeletal complication of sickle cell-mediated microvascular occlusion —> bone infarction
bones are susceptible to bone infection (osteomyelitis) by unusual organisms, especially salmonella
describe the renal complications of sickle cell disease
sickle cell nephropathy - renal medulla is most susceptible to hypoxic injury
renal papillary necrosis (papillae and inner medulla) - most commonly due to ischemia injury, usually bilateral —> flank pain and hematuria
describe how autosplenectomy occurs in patients with sickle cell disease
what does this put patients at risk for?
early in childhood, spleen enlarges
recurrent splenic infarction (from constantly trapping and pooling sickle RBC) —> scarring and fibrosis
eventually, spleen shrinks and stops working —> autosplenectomy
functional hyposplenism —> increased risk to encapsulated organisms (salmonella)
what is the leading cause of death in patients with sickle cell disease?
acute chest syndrome (ACS): vaso-occlusion of pulmonary vasculature, causing hypoxemia
what are 4 management strategies for sickle cell disease?
- avoid vaso-occlusion (induced by altitude, dehydration)
- folic acid supplements: can be depleted by high RBC turnover
- vaccination against encapsulated organism (while spleen is still functioning)
- hydroxyurea: increases HbF production, decreased HbA synthesis
hydroxyurea increases HbF synesthesia while decreasing HbA synthesis by selectively inhibiting…
ribonucleotide diphosphate reductase (needed for DNA synthesis)
end up with more favorable concentration of HbF vs HbS in patients with sickle cell disease
under what condition does HbS hemoglobin sickle and polymerize (become “sticky”)?
deoxygenation
risk of sickling increase with low oxygen and dehydration
what is hemoglobin C disease caused by?
Glu —> Lys mutation = HbC
reduced RBC survival, more rigid, blood more viscous
mild hemolysis —> borderline area and splenic enlargement
HbC presents like sickle cell trait
(type of inherited hemolytic anemia)
what are the 2 types of antibody-mediated hemolytic anemia?
warm: antibodies react at body temp, IgG mediated
cold: antibodies react at lower temp (at extremities), IgM mediated
describe what occurs in warm autoimmune hemolytic anemia (AIHA)
IgG coat RBC
spleen macrophages have Fc receptors, which causes extravascular hemolysis of RBC
—> splenomegaly and spherocytes development (which don’t survive well)
50% of warm autoimmune hemolytic anemia (AIHA) are idiopathic, 50% are associated with an underlying condition
what might these be?
remember Immune Mediated RBC Lysis:
1. Infection (esp. in children)
2. Medications
3. Rheumatologic/autoimmune (SLE)
4. Lymphoproliferative disorders (leukemia)
what test is needed to diagnose warm AIHA? (autoimmune hemolytic anemia)
direct Coomb’s test - detects antibody or C3b bound to RBCs (via antibody, which causes RBC to agglutinate)
generally test results will be positive for both anti-IgG and anti-C3 (binds RBC but isn’t activated)
what are the first-line treatments for warm AIHA (autoimmune hemolytic anemia)?
- glucocorticoids
- splenectomy
- rituximab: anti-CD20, kills B cells
what additional problem does cold AIHA induce as compared to warm AIHA? explain why this makes sense
cold AIHA (autoimmune hemolytic anemia): IgM mediated, binds at lower temp (like at extremities)
IgM and RBC interaction causes RBC agglutination - this makes sense because IgM (pentamer) is bigger than IgG (which mediates warm AIHA)
C3b binds RBC and complement is activated —> Kupffer cells in liver cause extravascular hemolysis (have C3b receptors)
RBC are trapped in liver, not spleen, and RBC are fully phagocytosed, so no spherocytes are seen
in what kind of anemia is complement activated, which causes full phagocytosis by Kupffer (macrophages) cells in the liver, leading to extravascular hemolysis?
cold AIHA (autoimmune hemolytic anemia): IgM mediated, C3b binds
Kupffer cells have Fc receptors for C3b
spherocytes are not seen because cells are fully phagocytosed
(unlike in spleen, where bits of membrane are torn off, creating spherocyte)
how does vascular occlusion due to RBC agglutination in cold AIHA (autoimmune hemolytic anemia) present?
acrocyanosis: dark purple, gray, or hyperpigmented skin at extremities (fingers, toes)
necrosis can occur
what kind of infections are associated with cold AIHA? (autoimmune hemolytic anemia)
bacterial and viral infections in YOUNG patients
mycoplasma pneumoniae
Epstien-Barr virus (mononucleosis)
in older patients: lymphoid malignancy
how will direct Coomb’s test differ for warm vs cold AIHA?
warm AIHA: positive for anti-IgG and anti-C3
(extravascular hemolysis in spleen)
cold AIHA: positive for anti-C3 ONLY
(extravascular hemolysis in LIVER)
what are 2 treatments are for symptomatic patients with cold AIHA?
- rituximab: anti-CD20, kills B cells
- sutimlimba: anti-C1s (complement)
splenectomy is NOT effective because it is the LIVER that causes extravascular hemolysis
describe the cause of paroxysmal nocturnal hemoglobinuria. what kind of disease is this?
non-immune mediated acquired hemolytic anemia
acquired mutation in PIGA gene on X chromosome - PIGA generates GPI for links for surface proteins (glycosyl-phosphatidylinositol)
mutation occurs in hematopoietic stem cells —> affects all blood cells (but mixed population of affected cells)
what is the effect of an acquired PIGA mutation as seen in paroxysmal nocturnal hemoglobinuria, a non-immune mediated acquired hemolytic anemia?
PIGA (X chromosome) generates GPI-linked protein for cell surface, which are inactivators of complement:
*CD55: inactivates C3 convertase
*CD59: inactivates MAC
RBC that lack CD55 and CD59 are susceptible to complement lysis
a mutation in PIGA gene that makes cells susceptible to complement-mediated lysis
paroxysmal nocturnal hemoglobinuria: non-immune mediated acquired hemolytic anemia
hematopoietic stem cells lack CD55 (dissociates C3 convertase) and CD59 (prevents MAC formation) on cell membrane
describe the presentation of paroxysmal nocturnal hemoglobinuria? why is it called this?
paroxysmal + nocturnal hemolysis: there is increased CO2 arterial pressure at night, and therefore lower pH —> complement activation
patients have anemia + intravascular hemolysis (hemolysis is MAC/complement mediated)
2 major effects of free hemoglobin
- generates ROS
- scavenges/depletes NO (vasodilator)
the leading cause of death in patients with paroxysmal nocturnal hemoglobinuria?
thrombosis - complement activation increases risk of venous thrombosis (esp. DVT)
remember that PNH is non-immune mediated acquired hemolytic anemia
what will diagnostic labs indicated for paroxysmal nocturnal hemoglobinuria (PNH)?
remember PNH is non-immune mediated acquired hemolytic anemia
signs of intravascular hemolysis: high LDH (lactate dehydrogenase), low haptoglobin, positive urine hemoglobin
NEG direct Coombs test (NOT immune-mediated)
confirm diagnosis with flow cytometry - look for presence of CD55 and CD59 on cell membranes (absent in PNH)
what anemia does eculizumab treat and what does it do?
treats PNH (paroxysmal nocturnal hemoglobinuria), a non-immune acquired hemolytic anemia (intravascular)
eculizumab binds CD5 and prevents MAC formation
(remember that hemolysis in PNH is complement mediated, because CD55 and CD59 are not present on blood cells)
fragmentation hemolysis
mechanically-acquired hemolytic anemia
due to direct trauma
or
associated with vascular abnormality - intravascular device or valve defect, altered blood vessel
results in intravascular hemolysis
what is “march” hemoglobinuria?
(rare) direct trauma to RBC that results in mechanically-acquired hemolytic anemia
occurs in soldiers after long marches or runner due to direct trauma to RBCs in vessels of feet
can cause RBC fragmentation
how can microthrombi formation cause RBC fragmentation and mechanically-acquired hemolytic anemia?
RBC try to move through microthrombi and are sheered/fragmented in the process
*these patients show signs of intravascular thrombosis AND low platelet count (because platelets are consumed in thrombosis)
