Lectur 5 in hematology by Dr.Alaa fadhil Alwan
The Inherited Hemolytic Anemias
Hemolytic anemias are characterized by premature destruction of erythrocytes (hemolysis).
Clinically, they are recognized by an increase in the reticulocyte count
There are many different types of hemolytic anemia. At the most basic level, hemolytic
anemias can be divided into conditions that are intrinsic to the erythrocyte and those that are
extrinsic to the erythrocyte. Virtually all hemolytic anemias that are intrinsic to the
erythrocyte are inherited, and virtually all hemolytic anemias that are extrinsic to the
erythrocyte are acquired.
Sickle Cell Anemia (Hemoglobin S)
Epidemiology
Hemoglobin S (sickle hemoglobin) is the most common hemoglobinopathy worldwide.
Hemoglobin S is found most frequently in equatorial Africa and in people of African descent.
There are separate pockets of hemoglobin S in Turkey, along the Mediterranean coast (Sicily,
southern Italy, and northern Greece), in Saudi Arabia. These are areas where falciparum
malaria is endemic; suggesting that hemoglobin S arose as a protective mechanism against
malaria.
Pathophysiology
The abnormality in Hb S is substitution of valine for glutamic acid at the sixth amino acid
position. Deoxygenated hemoglobin S tends to polymerize into long rigid structures, which
distort the cell into the characteristic sickle shape. Anything that causes deoxygenation of
hemoglobin predisposes to sickling, including hypoxia, acidosis, and increased temperature.
The polymerization of hemoglobin S is reversible, and cells that have sickled may return to
normal shape with re-oxygenation. However, the repeated cycles of sickling and unsickling
damage the cell, and, eventually, the erythrocytes becomes irreversibly sickled. The rigid
elongated sickle cells obstruct small blood vessels, resulting in tissue infarction. Sickled
erythrocytes are also “sticky” and adhere to endothelial cells, predisposing to thrombosis.
Common sites of infarction include the spleen, bone and bone marrow, the medulla of the
kidney, mesenteric vessels, and pulmonary vessels.
Clinical Manifestations and Complications of Sickle Hemoglobin
Heterozygosity for hemoglobin S (hemoglobin AS) is designated sickle cell trait. Sickle cell
anemia is the preferred term for people who are homozygous for hemoglobin S (hemoglobin
SS). The term sickle cell disease indicates patients with clinical evidence of sickling and
includes sickle cell anemia (hemoglobin SS), sickle/hemoglobin C (hemoglobin SC, and
sickle/alfa-thalassemia Since people with sickle trait are asymptomatic, sickle cell trait is not
considered a sickle cell disease.
People who are heterozygous for hemoglobin S (hemoglobin AS) are generally
asymptomatic, have a normal blood hemoglobin level and complete blood count (CBC), and
have a normal life span.
Homozygous Hemoglobin S (Sickle Cell Anemia): The severity of illness in sickle cell
anemia (hemoglobin SS) is highly variable and can vary even within families. Many children
become symptomatic in infancy after 3 to 4 months of age (before that time they are protected
by the high levels of hemoglobin F). Other people have very mild disease and may not be
diagnosed until adulthood. The reasons for this variability are not clear; the level of
hemoglobin F is a factor (an increase in hemoglobin F decreases the severity of sickle cell
disease), but other factors also appear to be important.
People who are heterozygous for both hemoglobin S and some other hemoglobinopathy
(hemoglobin C, hemoglobin, or who are heterozygous for hemoglobin S and alfa-thalassemia,
are often symptomatic and may have many of the same complications as homozygous sickle
cell anemia..
Sickle Cell Crises
Three major categories of sickle cell crises have been identified:
1. Acute vaso-occlusive (painful) crises: Painful crises are the most common type of crisis
and are believed to be caused by occlusion of small blood vessels, with consequent infarction
of tissues.
2. Sequestration crises: Sequestration crisis can occur during childhood, usually during the
first 3 to 4 years, before the spleen has become infarcted. The spleen suddenly becomes
enlarged and engorged with blood; this can sequester a major portion of the total blood
volume and can be fatal.
3. Acute aplastic crises: This occurs as a complication of infections, usually but not always
due to parvovirus B19. Acute parvovirus B19 infection causes a transient stop in production
of erythrocytes, which usually lasts about 5 to 7 days.
Other Complications of Sickle Cell Disease
1. Infections: Infections are the most common cause of death in sickle cell disease.
Overwhelming pneumococcal sepsis is the major risk, due to impaired splenic function and
splenic auto-infarction. Starting in infancy, children with sickle cell anemia are usually
maintained on penicillin prophylaxis against pneumococcal sepsis. Gram-negative rods are
the most common type of infectious agent in adults. Osteomyelitis is common in patients with
sickle cell anemia
2. Cerebrovascular accidents: Strokes are a major cause of morbidity in sickle cell disease,
occurring in 5 to 8% of patients by the age of 14 years. They usually occur in young patients,
with a median age below 10.
3. Acute chest syndrome (acute lung syndrome): The acute chest syndrome is the second most
common cause of hospitalization (after vasoocclusive crises) and causes approximately 25%
of the deaths from sickle cell disease.Manifestations include pulmonary infiltrates on chest
radiograph, fever, chest pain, hypoxemia, tachypnea, cough, and dyspnea.Infection, fat
embolism from infarcted bone marrow, other pulmonary embolism or vascular occlusions,
hypoventilation and atelectasis due to rib infarcts or surgery, and pulmonary edema are all
possible causes of the acute chest syndrome
4. Altered splenic function and splenic infarcts: Infants and young children with sickle cell
anemia often have mild splenomegaly. Later, sickling in the spleen leads to progressive
splenic infarction, and by adulthood, the spleen is typically reduced to a small fibrous nodule
(autosplenectomy)..
5. Renal disease: Infarction of the medulla of the kidney is common, resulting in hematuria
(gross or microscopic) and loss of concentrating ability.
6. Priapism: Priapism is a common problem in males with sickle cell anemia, due to infarction
of the corpora cavernosa of the penis. Repeated episodes result in impotence.
7. Gallstones: (pigment) gallstones are common in sickle cell disease, due to increased
hemoglobin turnover and bilirubin production;
8. Leg ulcers
9. Aseptic necrosis of the femoral heads
10. Retinopathy
11. Complications of pregnancy: The maternal mortality rate is increased. They also have an
increased rate of spontaneous fetal loss and low birth weight infants.
Diagnosis of Sickle Hemoglobin
Patients with sickle trait have a normal CBC and blood smear. The blood smear shows target
cells and the characteristic sickled erythrocytes with sharply pointed ends. Howell-Jolly
bodies may be present after splenic infarction, and nucleated red blood cells (RBCs) may be
present. Common tests for sickle hemoglobin include sickle solubility tests and hemoglobin
electrophoresis. The solubility test is usually positive if hemoglobin S comprises more than
10 to 20% of the hemoglobin. It is positive in patients with both sickle trait and sickle cell
anemia and therefore cannot be used to distinguish homozygous from heterozygous
hemoglobin S. The other test commonly used to detect hemoglobin S is hemoglobin
electrophoresis
Treatment of Sickle Cell Disease
General supportive measures, including folic acid supplementation and prophylactic
penicillin, are important. Prophylactic penicillin has been shown to reduce mortality from S.
pneumoniae, and should be started as soon as possible after birth and continued at least
through age 5 years. Febrile episodes must be presumed to represent sepsis until proven
otherwise and managed accordingly.
Treatment of acute painful vaso-occlusive crises is predominantly supportive; the key
measures are adequate hydration and pain control. Morphine is generally the preferred
parenteral agent for severe pain....
Red cell transfusions should be considered for acute cerebrovascular accidents, intractable or
recurrent episodes of the acute chest syndrome, or priapism that does not respond to
conservative measures. Exchange transfusion allows the hemoglobin S concentration to be
decreased rapidly and is helpful in such instances
The acute chest syndrome is treated with supplemental oxygen, empiric antibiotics pending
culture results, adequate analgesia, and transfusions as needed.
An important advance in preventive therapy is the use of hydroxyurea. Hydroxyurea has been
shown to decrease the number of painful crises, hospitalizations, red cell transfusions, and
episodes of the acute chest syndrome in patients with sickle cell anemia. Hydroxyurea
increases the percent of fetal hemoglobin in the erythrocytes of many patients, which
interferes with polymerization of hemoglobin S and therefore decreases sickling, but, the use
of a chemotherapy drug for a non-neoplastic condition has raised a concern regarding
possible carcinogenic (particularly leukemogenic) potential, especially in children
Transfusion therapy in sickle cell disease: The anemia in sickle cell disease is usually well
compensated and does not require transfusions. Red cell transfusion to maintain hemoglobin
S levels <30% is recommended for patients who have had cerebrovascular accidents and is
commonly used in acute cerebrovascular accidents, acute chest syndrome, and priapism that
does not respond to conventional therapies.
Stem cell therapy (bone marrow transplant): Bone marrow transplant (BMT) or other
hematopoietic stem cell therapy has the potential of completely reversing the abnormality in
sickle cell disease. Bone marrow transplants have been performed in a number of patients,
with generally favorable results
THE THALASSEMIAS
The thalassemias are characterized by a quantitative abnormality of globin chain synthesis.
Classic thalassemia is characterized by a complete lack of globin chain synthesis or a
decreased amount of a structurally normal globin chain. The majority of thalassemias involve
either the alfa or beta globin chains. There is a high prevalence of thalassemia in areas with
endemic malaria, including parts of Africa, the Mediterranean basin, the Middle East, India,
Southeast Asia, and southern China (the “thalassemia belt”). Epidemiologic evidence
suggests that the thalassemias arose as a defense against malarial infection,
The decrease in globin chain synthesis has two consequences:
1• Decreased hemoglobin synthesis, resulting in anemia and microcytosis
2• Aggregation of the excess free globin chains produced by the non-thalassemic gene (alfa
chains in the case of beta thalassemia; beta chains in the case of alfa thalassemia). The
aggregates of unpaired globin chains attach to and damage the erythrocyte cell membrane,
resulting in hemolysis. In severe cases, the majority of erythroid precursors are destroyed in
the marrow (ineffective erythropoiesis). Those that escape into the circulation are prematurely
destroyed by macrophages in the spleen and liver.
Complications of Thalassemias
The complications of thalassemia are related to four factors:
1• Chronic anemia: Chronic anemia causes growth retardation, delayed sexual maturation,
cardiac dilatation and congestive heart failure, decreased work capacity, and all of the other
complications associated with chronic anemia.
2• Marked expansion of the bone marrow: The bone marrow becomes greatly expanded due
to marked erythroid hyperplasia. Widening of the diploic spaces in the skull gives a
characteristic “hair on end” appearance on radiographs. Hypertrophy of the frontal bones
results in frontal bossing. Hypertrophy of the maxillae results in prominent Cheeks and dental
malocclusions, giving a characteristic “chipmunk” facies. Extramedullary hematopoiesis
causes enlargement of the spleen and liver.
3• Iron overload: There is chronic hyperabsorption of iron by the gastrointestinal tract. Iron
deposition in the heart causes cardiomyopathy and cardiac arrhythmias. Deposition in the
liver causes portal fibrosis and may result in hepatic cirrhosis. Patients with hepatic cirrhosis
are at risk of developing hepatocellular carcinoma (hepatoma).
4• Chronic hemolysis: Chronic hemolysis causes splenomegaly, hepatomegaly, and bilirubin
gallstones. Hypersplenism may develop, increasing transfusion requirements.
The clinical manifestations of the different types of thalassemia (alfa versus Beta ) are
generally similar.
Alfa -Thalassemia
Pathophysiology
Most cases of alfa-thalassemia are due to deletions in the alfa globin genes. There are two
genes for the alfa globin chain on chromosome 16; the mutation may involve only one or both
alfa genes on each chromosome. Since each person has four alfa genes, there can be a
deletion in one, two, three, or all four alfa genes. The severity of illness depends on the
number of alfa genes with mutations.
• Single-gene mutation (αα/α-): Clinically silent, without microcytosis or anemia
• Two-gene mutation (-α/-α or ––/αα; α-thalassemia minor or α-thalassemia trait): Mild
microcytic anemia; serious complications are uncommon
• Three-gene mutation (αα/-α; hemoglobin H disease): Moderately severe, microcytic anemia.
The excess β chains precipitate as β4 tetramers (hemoglobin H). The clinical picture is
variable; patients may or may not have splenomegaly, iron overload, and the skeletal
complications seen in severe thalassemia.
• Four-gene mutation (––/––; hydrops fetalis): Incompatible with life.
Beta -Thalassemia
Pathophysiology
There is a single gene for the beta globin chain on chromosome 11. Most mutations in beta-
thalassemia are single-nucleotide substitutions. The mutation may result in a complete lack of
beta chain synthesis (β
0
-thalassemia) or a decrease in beta chain synthesis (β
+
-thalassemia).
The severity of illness depends on how much β chain is synthesized and whether the person is
heterozygous or homozygous for the mutation. The β –thalassemias have been divided into
three main clinical syndromes:
1• β -Thalassemia minor: Heterozygosity for β–thalassemia results in a mild clinical
syndrome called β -thalassemia minor. The hemoglobin and the MCV are mildly or
moderately decreased (hemoglobin ~9–12 g/dL and MCV ~65–75 fL), and the patient has few
symptoms or complications.
2• β -Thalassemia major (Cooley’s anemia) (Homozygosity for β -thalassemia results in a
severe clinical syndrome characterized by severe anemia and microcytosis (hemoglobin ~3–5
g/dL and MCV <65 fL), total or near total absence of Hb A, marked ineffective
erythropoiesis, marked expansion of the bone marrow with skeletal complications,
splenomegaly, and iron overload due to hyperabsorption of iron.
3• β -Thalassemia intermedia: beta-Thalassemia intermedia is homozygous beta-thalassemia
that is not transfusion dependent. It is genetically and clinically heterogeneous. The
hemoglobin is intermediate between β –thalassemia major and minor (~6–9 g/dL), as is the
incidence of clinical complications.
Diagnosis of Thalassemia
A microcytic anemia that is not due to iron deficiency is most likely thalassemia. The first
step after identification of a microcytic anemia is to check the serum ferritin or serum
iron/transferrin/transferrin saturation. If the results do not indicate iron deficiency, start a
workup for thalassemia which includes history of ethnic background and family history,
examination of a well-stained blood smear, and hemoglobin electrophoresis.
The blood smears in mild thalassemia shows microcytosis, hypochromia, and target cells.
There may be basophilic stippling. In more severe cases, there is marked microcytosis and
anisocytosis, bizarre poikilocytes, polychromasia, and nucleated erythrocytes.
β -Thalassemia is generally diagnosed by the presence of increased hemoglobin A2 on
hemoglobin electrophoresis. Hemoglobin F is often also slightly increased. The mean
hemoglobin A2 level in β -thalassemia is about 5% (normal is less than about 3%).
Alfa-Thalassemia trait (two gene mutations) is generally diagnosed by exclusion: a microcytic
anemia that is not due to iron deficiency and has normal hemoglobin A2 is most likely alfa-
thalassemia. The hemoglobin electrophoresis is normal, except for the first few weeks of life,
when four gamma tetramers (hemoglobin Bart’s) are present. Study of family members can
also be helpful in confirming the suspicion of alfa-thalassemia. Hemoglobin H disease can be
diagnosed by the presence of hemoglobin H on electrophoresis.
Prenatal Diagnosis of Thalassemia
Molecular analysis of the globin genes for thalassemia can be done on amniotic cells obtained
by amniocentesis or on chorionic villus cells obtained by chorionic villus biopsy.
Treatment of Thalassemia
The cornerstones of thalassemia therapy are red cell transfusion and iron chelation. Patients
with thalassemia minor usually do not require transfusion just folic acid tab. Patients with
thalassemia intermedia or hemoglobin H disease may or may not require transfusions to
prevent complications of anemia and erythroid hyperplasia. Patients with severe thalassemia
are frequently maintained on hypertransfusion regimens in which periodic red cell
transfusions given to maintain the blood hemoglobin >9 to 10 g/dL. This prevents the skeletal
complications of thalassemia by shutting off the erythropoietin-driven erythroid hyperplasia,
allows normal growth and sexual development, and delays the onset of splenomegaly. A
typical transfusion requirement is one to three donor units every 3 to 5 weeks.
Iron overload is a serious complication of transfusion therapy (each red cell unit contains
200–250 mg of iron), and chelation therapy is required to prevent the development of
secondary hemochromatosis Splenomegaly eventually develops in patients with severe
thalassemia even with transfusion therapy, and splenectomy will be required. The usual
indication for splenectomy is an increase in transfusion requirement. Bone marrow transplant
is potentially curative for thalassemia. Patients with related HLA-matched donors and severe
thalassemia should be considered for BMT early, before serious complications occur .
RED CELL ENZYME DEFECTS
Some defects in erythrocyte metabolic enzymes are associated with hemolytic anemia. By far
the most common of these is glucose-6-phosphate dehydrogenase (G6PD) deficiency.
Glucose-6-Phosphate Dehydrogenase Deficiency
Epidemiology
Glucose-6-phosphate dehydrogenase deficiency is one of the most common genetic diseases
in the world, affecting hundreds of millions of people. The gene for G6PD is located on the X
chromosome, so G6PD deficiency is inherited as an X-linked trait. As for all X-linked traits,
men develop the disease, whereas women are usually asymptomatic carriers. It is most
common in areas of endemic malaria, and it (like sickle hemoglobin and the thalassemias)
probably arose as a defense mechanism against malaria.
Pathophysiology
G6PD is the first enzyme in the hexose monophosphate shunt, in the absence of sufficient
glutathione, hemoglobin is oxidized and precipitates in the cell. This damages the cell,
resulting in hemolysis. The aggregates of oxidized hemoglobin are taken out of the cell by the
spleen, resulting in characteristic “bite” or “blister” cells. The level of G6PD is highest in
reticulocytes and declines with increasing age of the red cell.
Clinical Manifestations of G6PD Deficiency
The clinical severity of G6PD deficiency is variable. The majorities of patients are not anemic
and have no hemolysis in the baseline state; minorities of patients have chronic, ongoing
hemolysis. It is likely that the majority of people with G6PD deficiency are never diagnosed
as such.. Under normal conditions, patients have no hemolysis or anemia. Episodes of
hemolysis may be precipitated by infection, oxidative drugs or chemicals, surgery, and
acidosis. Infections are probably the most common cause of hemolytic episodes. Most
infection-associated hemolytic episodes are self-limited and mild, although fulminant
hemolysis with disseminated intravascular coagulation and acute renal failure can occur.
Drugs and chemicals that can cause hemolysis include primaquine and other antimalarial
agents, sulfa antibiotics, naphthalene and phenazopyridine . Episodes of hemolysis are
indicated by sudden onset of jaundice, pallor, dark urine, and abdominal or back pain. The
hemoglobin level typically drops about 3 to 4 g/dL. The blood smear may show “bite” and
“blister” cells, polychromasia, schistocytes, and microspherocytes.
Serum bilirubin and lactic dehydrogenase levels are increased; haptoglobin is decreased. A
reticulocyte response becomes evident at about 5 days and is maximal at 10 days. Since
reticulocytes have protective G6PD levels, hemolysis stops, and the hemoglobin returns to
normal after about 2 to 4 weeks even if the oxidative drug is continued. Uncooked fava beans
are a notorious cause of hemolysis in patients with G6PD Mediterranean (favism).
Diagnosis of Glucose-6-Phosphate Dehydrogenase Deficiency
Glucose-6-Phosphate Dehydrogenase deficiency should be an important consideration
in any case of acute nonimmune hemolytic anemia. The peripheral smear should be examined
for ‘bite” or “blister” cells and cells with eccentric “puddles” of hemoglobin; however, the
smear is often surprisingly normal.
➪ The G6PD level can be normal in a patient with G6PD deficiency shortly after a hemolytic
episode, giving a false-negative result. This occurs if the reticulocyte count is high since
reticulocytes have higher G6PD levels than older cells. If you get a normal G6PD level in a
patient who you really think has G6PD deficiency, repeat the laboratory test in a few weeks.
Treatment of Glucose-6-Phosphate Dehydrogenase Deficiency
The main treatment for G6PD deficiency is to avoid conditions that predispose to hemolysis.
Patients with G6PD deficiency should not be given medications that cause hemolysis.
Infections should be treated promptly .give folic acid tab
The Red Cell Membrane defect
Hereditary Spherocytosis
Epidemiology
Hereditary spherocytosis (HS) is the most common inherited hemolytic anemia in people of
Northern European descent inherited in an autosomal dominant fashion
Pathophysiology
The fundamental cause in most cases of HS is defective vertical attachment between the
phospholipid bilayer and the cytoskeleton scaffold. Hereditary spherocytosis is genetically
and clinically heterogeneous; the majority of cases result from mutations in the gene for
ankyrin. Spherocytic RBCs are less flexible than normal (biconcave disk) RBCs, and,
consequently, they are selectively trapped and destroyed in the spleen.
Clinical Manifestations
The clinical manifestations of HS are highly variable, from asymptomatic without anemia to
severe chronic hemolysis.. The majority of older patients have relatively mild or moderate
anemia, and the primary manifestations are hyperbilirubinemia (which may be intermittent)
and mild splenomegaly. Bilirubin gallstones are common. Like other patients with chronic
hemolytic anemias, patients with HS may have exacerbation of anemia associated with
infections, aplastic crises due to parvovirus B19 infection, or megaloblastic anemia associated
with folate deficiency.
Diagnosis of Hereditary Spherocytosis
The CBC shows a MCV that is normal to slightly low, with an increased mean corpuscular
hemoglobin concentration (MCHC). The blood smear shows microspherocytes .The
reticulocyte count is increased A direct antiglobulin (Coombs’) test should be done to exclude
an immune hemolytic anemia.
• A hemolytic anemia with spherocytes with a negative direct antiglobulin test is most likely
HS. The classic laboratory test for HS is the osmotic fragility test.
• It is important to remember that increased osmotic fragility is not specific for HS; any cause
of spherocytosis results in increased osmotic fragility.
Treatment of Hereditary Spherocytosis
The standard treatment for HS is splenectomy. Since the spleen is involved in both, causing
the membrane loss and removing the spherocytes from the circulation, splenectomy is highly
effective. However, because of the risk of overwhelming infection following splenectomy,
splenectomy should be performed only on patients having significant complications from
anemia, such as growth retardation. It should be delayed until at least 3 to 5 years of age if
possible. Folic acid supplementation is also recommended
Acquired Hemolytic Anemias
Acquired hemolytic anemias are divided into two main types: immune and non-immune.
Unlike the inherited hemolytic anemias, which predominantly involve abnormalities intrinsic
to the erythrocyte, the acquired hemolytic anemias (with one exception) involve abnormalities
that are extrinsic to the erythrocyte. The exception to the acquired extrinsic rule is
paroxysmal nocturnal hemoglobinuria (PNH), which is an acquired genetic lesion resulting in
increased susceptibility of red blood cells (RBCs) to hemolysis by the complement cascade.
IMMUNE HEMOLYTIC ANEMIAS
The easiest way to approach the immune hemolytic anemias is to divide them according to the
mechanism of hemolysis and the type of mediating antibody:
• Warm-reactive antibodies, usually immunoglobulin G (IgG), versus cold-reactive
antibodies, usually IgM
Immune hemolytic anemias can be further divided: (1) primary or idiopathic versus secondary
and (2) acute versus chronic. An important additional category of immune-mediated
hemolysis is immune hemolytic anemia due to drugs or medications.
Cold-Reactive Immune Hemolytic Anemia
Cold-reactive immune hemolytic anemia is generally mediated by IgM antibodies that react
maximally at approximately 4 to 18ºC. They bind to cells at the cooler temperature of the
extremities, fix complement, and then dissociate from the cell surface after the RBC returns to
the warmer temperatures of the central circulation. The complement components remain on
the cell surface after the antibody dissociates. IgM antibodies may cause intravascular
hemolysis if the antibody is present in high titer; more often hemolysis is extravascular,
predominantly in the liver. IgM antibodies are large and can bridge the distance between two
RBCs; thus, IgM antibodies by themselves are able to agglutinate RBCs. (In contrast, IgG
antibodies are smaller and alone are not able to agglutinate RBCs.) There are many causes of
cold-reactive immune hemolytic anemia Most of these fall into the category of cold agglutinin
disease. Cold agglutinin disease, in turn, is divided into primary (idiopathic) and secondary
forms. Cold-reactive immune hemolytic anemia is less common than the warm-reacting type,
accounting for approximately 10 to 20% of immune hemolytic anemia.
Causes of Cold-Reactive Immune Hemolytic Anemia
Cold agglutinin disease:
• Primary (idiopathic)
• Secondary:
Infections
Autoimmune disorders
Lymphoproliferative disorders
Paroxysmal cold hemoglobinuria (PCH)
Primary (Idiopathic) Cold Agglutinin Disease
Primary cold agglutinin disease occurs with no obvious precipitating cause. It usually occurs
in older individuals (peak age about 70 years) and is more common in women than men. The
course is usually chronic, lasting for months or years. The anemia associated with idiopathic
cold agglutinin disease is usually modest; the main symptoms are related to agglutination of
erythrocytes on exposure to cold rather than the anemia. Agglutination occurs in the fingers,
toes, nose, and ears and causes cyanosis of those areas (acrocyanosis). Some patients have a
lymphoproliferative disorder such as chronic lymphocytic leukemia (CLL), Waldenström’s
macroglobulinemia, or non-Hodgkin’s lymphoma.
Secondary Cold Agglutinin Disease
Secondary cold agglutinin disease is most often related to infections, primarily Mycoplasma
pneumoniae or Epstein-Barr virus (EBV) (infectious mononucleosis). It can occasionally
occur with other viral infections (adenovirus, cytomegalovirus, rubella, mumps, HIV),
bacterial infections (Legionella, Escherichia coli, Listeria), malaria, syphilis, and others. The
patients are usually young and otherwise healthy. The onset is abrupt, usually as the infection
is resolving. The patients present with pallor, jaundice,
and the other signs of acute hemolytic anemia. Massive acute intravascular hemolysis and
acute renal failure may occur but are fortunately rare. Infection- related cases tend to be
transient and self-limited, lasting only a few weeks.
Diagnosis of Cold Agglutinin Disease
Cold agglutinins cause several abnormalities on the routine CBC, including a decreased RBC
count, increased mean corpuscular volume (MCV), and increased mean corpuscular
hemoglobin concentration (MCHC). Large round clusters of RBCs are seen on the blood
smear. Repeating the CBC and smear after rewarming the sample to 37ºC resolves the
difficulties, demonstrating the temperature dependence of the reaction. Spherocytes may be
present on smear, particularly in cases of acute cold agglutinin disease related to infection. A
direct antiglobulin test (DAT or Coombs’ test) detects the presence of complement
components (but not IgG) on the surface of the patient’s RBCs.
Treatment of Cold Agglutinin Disease
Primary Cold Agglutinin Disease
Patients should avoid cold temperatures and take precautions to keep the extremities warm. In
patients who require further therapy, cyclophosphamide or chlorambucil given orally may be
helpful. Corticosteroids and splenectomy (the mainstays of therapy for warm immune
hemolytic anemia) are generally not helpful. Plasmapheresis to remove the agglutinin may
provide temporary benefit.
Secondary Cold Agglutinin Disease
Infection-related cold agglutinin disease is usually transient, lasting only a few weeks.
Supportive therapy is usually all that is needed.. It is important for the blood bank to test for
red cell antibodies other than the cold agglutinin (alloantibodies). If an alloantibody is
detected, units lacking the corresponding antigen should be chosen. It is
important to maintain the temperature of the transfused blood at 37ºC, using a blood warmer,
to prevent the transfused cells from agglutinating as soon as they enter the patient.
Warm-Reactive Immune Hemolytic Anemia
Warm-reactive immune hemolytic anemia is more common than the cold reactive variant. It
can be primary (idiopathic), secondary to a wide variety of different conditions, or drug-
related .Most cases (about 80%) are due to some underlying condition, although this may not
be apparent at the onset of hemolysis. Hemolytic anemia may be the presenting feature of
SLE or other autoimmune disorder.
The idiopathic variety is more common in women and the older population. The antibody is
almost always an IgG
Causes of Warm-Reactive Immune Hemolytic Anemia
Primary (idiopathic)
Secondary
Infections
Autoimmune disorders: SLE, rheumatoid arthritis
Lymphoproliferative disorders: CLL, non-Hodgkin’s lymphomas, myeloma
Hodgkin’s lymphoma
Thymoma
Ovarian dermoid cyst or teratoma
Carcinomas
Hypogammaglobulinemia
Acquired immunodeficiency syndrome (AIDS)
Drug related
Clinical Manifestations
The severity of illness varies from an asymptomatic increase in red cell turnover completely
compensated by increased marrow production to a fulminant illness with shock, and acute
renal failure. The majority of patients experience an insidious onset of fatigue, weakness, and
shortness of breath on exertion. Angina may be a presenting feature in older patients with
coronary artery disease. Jaundice may be present. Mild splenomegaly and hepatomegaly may
be present on examination, as well as mild lymphadenopathy; however, marked
hepatosplenomegaly or lymphadenopathy
suggests an underlying lymphoproliferative disorder. The course in adults tends to be chronic,
lasting months to years, with periodic exacerbations.
Diagnosis
The hemoglobin level is variable, from severely decreased to nearly normal. The MCV is
typically slightly increased due to reticulocytosis. The peripheral blood smear shows
polychromasia and microspherocytes; in severe cases, nucleated RBCs may be present. The
reticulocyte count increased. The bilirubin and lactic dehydrogenase are elevated, and the
haptoglobin is decreased.
The most important diagnostic test is the direct antiglobulin test (DAT), which is positive in
>95% of cases. The antibody screen (indirect antiglobulin test) is positive in about 80% of
cases.
Evaluation
Initial evaluation should focus on determining the severity of illness and discovering any
possible causes of a secondary hemolytic anemia. Key points to consider:
• Identify any drugs or medications that the patient has been taking. All medications that may
cause drug-related immune hemolytic anemia should be stopped as much as possible.
• Determine if the patient has had any transfusions, particularly within the past 3 months.
• History of pregnancies (including miscarriages or abortions) is critical in women.
Treatment
Any possible primary cause (such as an underlying autoimmune disease or
lymphoproliferative disorder) should be treated appropriately. It is preferable to avoid red cell
transfusions, but they should be given if needed. The blood bank will usually not be able to
find totally compatible units for transfusion but may be able to select least incompatible units.
The mainstay of initial therapy is corticosteroids, such as prednisone (1–2 mg/kg/day in
divided doses). Most patients show a response within 3 weeks. Corticosteroids block the
macrophage Fc receptors and thus prevent RBC phagocytosis. They can also decrease
antibody production by the spleen, but this takes several weeks. Prednisone is usually
continued at the original dose until the hemoglobin is 10 g/dL; the dose is then slowly tapered
over 3 to 4 months. About 80% of patients initially respond; however, about two-thirds of
responders relapse as the drug is tapered. Some patients can be maintained on no
corticosteroids or on a low dose. Patients requiring more than 10 to 20 mg of prednisone per
day, or patients having intolerable side effects on prednisone, should be considered for
splenectomy.
Splenectomy is the mainstay of therapy for patients who fail to respond to corticosteroids or
who require excessive doses to maintain remission.
Splenectomy eliminates the primary site of red cell destruction and also removes an important
site of antibody production. drugs like cyclophosphamide or azathioprine, intravenous
immunoglobulin, plasmapheresis, vincristine or vinblastine, and danazol. Intravenous
immunoglobulin and plasmapheresis may be helpful, but the effects are
transient
NON-IMMUNOLOGIC ACQUIRED HEMOLYTIC ANEMIAS
Causes of Non-immunologic Acquired Hemolytic Anemia
1. Mechanical trauma: Malfunctioning mechanical heart valve, Microangiopathic
hemolytic anemias: thrombotic thrombocytopenic purpura (TTP),hemolytic-uremic
syndrome (HUS), preeclampsia/eclampsia, malignant hypertension, disseminated
intravascular coagulation (DIC)
2. Acanthocytosis: Hereditary abetalipoproteinemia, End-stage liver disease, Severe
starvation, anorexia nervosa
3. Severe hypophosphatemia: Intravenous hyperalimentation lacking phosphorous
supplementation, Severe starvation, Alcoholism, Prolonged therapy with phosphate-
binding antacids
4. Wilson’s disease; copper poisoning
5. Oxidative drugs or chemicals
6. Severe burns
7. Venoms
8. Infections: Direct infection of erythrocytes: malaria, babesiasis, bartonellosis,
trypanosomiasis,Clostridium perfringens septicemia Other: gram-positive and gram-
negative septicemia, leptospirosis, Borrelia, others
9. Paroxysmal nocturnal hemoglobinuria (PNH)
Paroxysmal Nocturnal Hemoglobinuria
Pathophysiology
Paroxysmal nocturnal hemoglobinuria is an acquired genetic disorder that results in
increased susceptibility of RBCs to lysis by the complement system. The condition results
from an inability to synthesize the glycosyl phosphatidylinositol (GPI) anchor, which anchors
a variety of molecules on the surface of erythrocytes and other cells.
Clinical Manifestations
Paroxysmal nocturnal hemoglobinuria occurs at all ages from childhood to old age but is most
commonly diagnosed in the fourth and fifth decades. The course is highly variable, from
clinically benign to a chronic disabling disorder. The name paroxysmal nocturnal
hemoglobinuria derived from patients who experienced episodes of dark urine on awakening
from sleep; however, this classic presentation occurs in only about one-fourth of patients. The
majority of patients have an insidious onset of fatigue, weakness, and jaundice. The attacks
are not precipitated by exposure to cold, distinguishing PNH from paroxysmal cold
hemoglobinuria. Patients may experience abdominal or back pain, nausea, headaches,
malaise, and fever associated with exacerbations of hemolysis. Unexplained pancytopenia
may also be a presenting manifestation of PNH.
Complications
Paroxysmal nocturnal hemoglobinuria is associated with a number of significant
complications, including:
• Thromboemboli: Thrombotic disease is a common complication in PNH and Thrombi
predominantly occur in the venous system, including unusual sites such as the cerebral veins,
mesenteric veins, portal vein, and hepatic vein (Budd-Chiari syndrome), as well as in the
extremities. The reason for the increased risk of thrombosis in PNH is unknown.
• Infections: Patients with PNH may be at increased risk of infections due to leukopenia,
leukocyte dysfunction, or corticosteroid therapy.
• Iron deficiency: Chronic intravascular hemolysis with hemoglobinuria results in iron
deficiency, which further exacerbates the tendency for anemia.
• Leukopenia, thrombocytopenia, or pancytopenia: Nearly all patients with PNH develop
leukopenia, thrombocytopenia, or pancytopenia.
• Hemorrhage: Patients with PNH and severe thrombocytopenia are at increased risk for
hemorrhage.
• Transformation to acute myelogenous leukemia: Transformation to acute myelogenous
leukemia is a rare but well-known complication of PNH.
• Development of aplastic anemia
Diagnosis
The CBC shows anemia, which can vary from mild to severe. The anemia is usually mildly
macrocytic but can be microcytic and hypochromic if iron deficiency has developed.
Leukopenia and/or thrombocytopenia are common. Lactic dehydrogenase and bilirubin may
be elevated during exacerbations of hemolysis. A test for urine hemosiderin will be positive.
The traditional diagnostic tests are the acidified serum (Ham’s) test and the sucrose hemolysis
test. The sucrose hemolysis test is more sensitive, but the Ham’s test is more specific.
Demonstration of a decreased expression of GPI-anchored proteins on RBCs or leukocytes by
flow cytometry with CD55 and CD 59 has been shown to be more sensitive than either of
these tests
Treatment
Standard treatments for PNH include corticosteroids and androgens. Both are helpful in some
patients and should be tried. Patients who respond should be maintained on minimally
effective doses to avoid side effects.
Transfusions may be needed for severe anemia. Thrombotic episodes are treated with
anticoagulants or thrombolytic agents.
Bone marrow transplantation has been tried in a few younger patients with histocompatible
donors, and has been relatively successful.
Prognosis
The median survival in PNH is approximately 10 to 15 years.