hemolysis: premature destruction of the red cells

Hemolysis:

premature destruction of the red cells

RBC normally survive 90 to 120 days in the circulation.

Kind of hemolysis:

Extravascular Hemolysis: RBC prematurely removed from the circulation by macrophages, particularly those of the spleen and liver

intravascular hemolysis: less commonly, by disruption of their membranes during their circulation-------------------------------------------------The level of unconjugated bilirubin never exceeds 70 to 85 umol/L (4 to 5 mg/dL), unless liver function is impaired.

Hemoglubin

Heme globulin

Protopurphyrin Fe Aminoacide

Unconjugated bil

Conjugated bil

(LDH), particularly LDH-2, is elevated

Serum AST (SGOT) may be somewhat elevated, whereas ALT (SGPT) is not.Haptoglobin :

High concentration (~1.0 g/L) in the plasma (and serum)It binds specifically and tightly to the globin in hemoglobinCleared within minutes by the mononuclear phagocyte system.

Is decreased in patients with hepatocellular disease and increased in inflammatory states

plasma hemoglobin is increased in proportion to the degree of hemolysis

Plasma hemoglobin may be falsely elevated due to lysis of RBC in vitro

Hemosiderin appears 3 to 4 days after the onset of hemoglobinuria and may persist for weeks after its cessation.

glomerular permeability than myoglobin and is less rapidly cleared by the kidneys.

the urine is positive with the benzidine reaction:

Hemoglobinuria , Hematuria , myoglobinurea

The distinction between hemoglobinuria and myoglobinuria:

Can best be made by specific tests that exploit immunologic differences

Differences in solubility:

After centrifugation of an anticoagulated blood specimen, a reddish-brown color (Hb) normal in color (myoglobin)

Because of its higher molecular weight, hemoglobin has lower glomerular permeability than myoglobin and is less rapidly cleared by the kidneys.

Classification of Hemolytic Anemias

Intracorpuscular

1. Abnormalities of RBC interiora. Enzyme defectsb. Hemoglobinopathies (Chap. 106)2. RBC membrane abnormalitiesa. Hereditary spherocytosis etc.b. Paroxysmal nocturnal hemoglobinuria

Heredtary

Extracorpuscular

c. Spur cell anemia3. Extrinsic factorsa. Hypersplenismb. Antibody: immune hemolysisc. Microangiopathic hemolysisd. Infections, toxins, etc.

Acquired

In intracorpuscular types of hemolysis, the patient's RBC have an abnormally short life span in a normal recipient (with a compatible blood type), while compatible normal RBC survive normally in the patient. The opposite is true in extracorpuscular types of hemolysis.

INHERITED HEMOLYTIC ANEMIASDefects are often known at the genomic level

1- The membrane 2-The enzyme 3-Hemoglobin

Red Cell Membrane Disorders These are usually readily detected by morphologic abnormalities of the RBC on the blood film

Three types of inherited RBC membrane abnormalities:

1- Hereditary spherocytosis

2- Hereditary elliptocytosis 3- pyropoikilocytosis

4- hereditary stomatocytosis.

.

Hereditary spherocytosis

This condition is characterized by :DEFECT OF ONE PROTEIN OF CYTOSKELATONLOSS OF RBC MEMBRANE S/V DECREASE SPHEROCYTOSIS usually has an autosomal dominant1:1000 to 1:4500~20% autosomal recessive inheritance or a spontaneous mutation The disorder is sometimes clinically apparent in early infancy but often escapes detection until adult life.


CLINICAL MANIFESTATIONS • Anemia

1. anemia is usually mild or moderate and may even be absent in an otherwise healthy individual

2. erythroid hyperplasia of the bone marrowextramedullary erythropoiesis paravertebral masses visible on chest x-ray

3. episodes of relative erythroid hypoplasia precipitated by infections, particularly parvovirus, trauma, surgery, and pregnancy

• Splenomegaly 4. Splenomegaly is very common

5. The hemolytic rate may increase transiently during systemic infections, which induce further splenic enlargement.

• Jaundice("congenital hemolytic jaundice“) Jaundice may be intermittent and tends to be less pronounced in early childhoodpigmented gallstones are common

• Chronic leg ulcers

Laboratory:

•MCV: is usually normal or slightly decreased

•MCHC : is increased to 350 to 400 g/L

•Osmotic fragility test: increased

• PBS :spherocytes are usually detected as small cells without central pallor

•They will ordinarily not influence the osmotic fragility test unless they constitute more than 1 or 2% of the total cell population

•The autohemolysis test is also useful.


OSMOTIC FRAGILITY TEST


PATHOGENESIS : PROTEIN DEFICIENCY

Nearly all patients have a significant deficiency of spectrin

50% of patients have a defect in ankyrin

25% of patients have a mutation of protein 3

remaining 25% have mutations of spectrin, leading to impaired synthesis or self-association

b-spectrin deficiency is generally mild, with dominant inheritance

a-spectrin deficiency is severe, with a recessive inheritance pattern.

"conditioning“: the lipid bilayer is not well anchored when these proteins are defective part of it is lost by vesiculation resulting in a more spherical less deformable cell.

DESTRUCTION ON SPLEEN

"conditioning" produces a subpopulation of hyperspheroidal RBC in the peripheral blood.


DIFERENTIAL DIAGNOSIS:

1. Immune spherocytosis

2. Cirrhosis

3. In clostridial infections,

4. Certain snake envenomations

5. Glucose -6-phosphate dehydrogenase (G6PD) deficiency.


TREATMENT:

1- Splenectomy•corrects the anemia, although the RBC defect and its consequent morphology persist•The operative risk is low•splenectomy should be performed in symptomatic individuals• cholecystectomy should not be performed without splenectomy, as intrahepatic gallstones may result•Splenectomy in children should be postponed until age 4•Polyvalent pneumococcal vaccine should be administered at least 2 weeks before splenectomy

2- folic acid (1 mg/d) should be administered prophylactically.^

Hereditary elliptocytosis :

Oval or elliptic RBC are normally found in birds, reptiles, camels, and llamasautosomal dominant trait 1 per 4000 to 5000 people (similar to that of hereditaryacquired elliptocytosis : rarely in patients with MDS

PATOGENESIS :

1- Spectrin Def. 2- protein 4.1 Def.

PRESENTATION : MILD ANEMIA (HB>120 RET<4%

In 10 to 15% of patients with more severe abnormalities, the rate of hemolysis is substantially increased, with median survival times of RBC as short as 5 days and reticulocytes ranging up to 20%.

RBC destruction occurs predominantly in the spleen, which is enlarged in patients with overt hemolysis

Hemolysis is corrected by splenectomy.

Hereditary elliptocytosis

at least 25% and, more commonly, >75% of RBC are elliptic, with an axial ratio (width/length) of <0.78. Patients with hemolysis frequently have microovalocytes, bizarre-shaped RBC, and RBC fragments, all of which increase in number after splenectomy.

The degree of hemolysis does not correlate with the percentage of elliptocytes.

Osmotic fragility is usually normal but may be increased in patients with overt hemolysis.

Hereditary pyropoikilocytosis:

• rare disorder

• bizarre-shaped, microcytic RBC that undergo

disruption at temperatures of 44 to 45°C

• normal RBC are stable up to 49°C

• Hemolysis is usually severe

• recognized in childhood, and is partially responsive to

splenectomy.

Hereditary Stomatocytosis:cup-shaped RBC (concave on one face and convex on the other). This formation results in a slitlike central zone of pallor on dried smears.autosomal dominant pattern. RBC have an increased permeability to sodium and potassium

overhydrated stomatocytes, "hydrocytosis“ In some patients, the RBC are swollen with an excess of ions and water and a decreased mean corpuscular hemoglobin concentration (many of these patients lack the RBC membrane protein 7.2 (stomatin) These are true stomatocytes on dried smears.

dehydrated stomatocytes, "desiccytosis" or "xerocytosis"In other patients, the RBC are shrunken, with a decreased ion and water content and an increased mean corpuscular hemoglobin concentration Theas assume the morphology of target cells on dried smears

Osmotic fragility is increased in overhydrated stomatocytes and decreased in underhydrated stomatocytes RBC lacking Rh proteins (Rhnull cells) are stomatocytic and have a shortened life span

Sign & symptom :splenomegaly and mild anemia

Treatment: Splenectomy decreases but does not totally correct the hemolytic process.

Red Cell Enzyme Defects

The RBC loses its nucleus, ribosomes, and mitochondria and thus its capability for protein synthesis and oxidative phosphorylation.

ATP must be generated from the Embden-Meyerhof pathway to:

• Drive the cation pump that maintains the ionic milieu in the RBC. Preservation of hemoglobin iron in the ferrous (Fe2+) state

• For the renewal of the lipids in the RBC membrane. • About 10% of the glucose consumed by the RBC is metabolized

via the hexose-monophosphate shunt which protects both hemoglobin and the membrane from exogenous oxidants, including certain drugs

Defects in the Embden-Meyerhof Pathway may be restricted to RBC or not Mutations can result in no protein product, a dysfunctional product, or an unstable productThese enzymopathies have similar pathophysiologic and clinical featuresPatients present with a congenital nonspherocytic hemolytic anemia of variable severityThe RBC are often relatively deficient in ATP, resulting in a leak of potassium ion out of these cellsThese RBC are rigid and thus more readily sequestered by the mononuclear phagocyte system.pyruvate kinase (PK) deficiency and hexokinase deficiency are localized to the RBCGlucose phosphate isomerase deficiency and phosphoglycerate kinase deficiency also involve leukocytes


Defects in the Embden-Meyerhof Pathway Individuals with deficiency of triose phosphate isomerase have decreased levels of enzyme in leukocytes, muscle cells, and cerebrospinal fluid, and they have a progressive neurologic disorder. Some patients with phosphofructokinase deficiency have a myopathy.

Incidence: defects in the glycolytic pathway PK deficiency : 95% glucose phosphate isomerase deficiency: 4% Other 1%



Defects in the Embden-Meyerhof PathwayA number of different mutations result in PK deficiency.There is considerable variability in the clinical manifestations and laboratory findings among individuals reported as having PK deficiencyMost of these patients are compound heterozygotes who have inherited a different defective enzyme from each parent.autosomal recessive pattern: most ofen (the parents are entirely asymptomatic)Phosphoglycerate kinase deficiency is inherited as a sex-linked disorder|(male sever anemia female mild hemolytic anemia )


Defects in the Embden-Meyerhof PathwayCLINICAL MANIFESTATIONSAnemia jaundice splenomegaly

LABORATORY FINDINGS

•PBS normocytic (or slightly macrocytic), normochromic anemia with reticulocytosis.• In those with PK deficiency, bizarre erythrocytes, including spiculated cells, are noted on the peripheral smear, especially after splenectomy. •Spherocytes are usually absent; hence the term congenital nonspherocytic hemolytic anemia• the osmotic fragility of freshly drawn blood is usually normal•AUTOHEMOLYSIS TEST• Incubation brings out an osmotically fragile population of RBC, an abnormality not corrected by the addition of glucose.• specific enzymatic assays

Red Cell Enzyme DefectsDefects in the Embden-Meyerhof PathwayTREATMENT:•Most patients do not require therapy•Those with severe hemolysis should be given folic acid (1 mg/d)•Blood transfusions may be necessary during a hypoplastic crisis•Women with PK deficiency may become very anemic during pregnancy sometimes leading to the diagnosis for the first timesplenectomy•PK•glucose phosphate isomerase•not been proven effective in individuals with other glycolytic enzymopathies.

Red Cell Enzyme Defects:

Defects in the hexose-monophosphate shuntGlucose metabolism via the hexose-monophosphate shuntReduced glutathioneprotecting the sulfhydryl groups of hemoglobin and the RBC membrane from oxidation

inherited defect in the hexose-monophosphate shununable to maintain an adequate level of reduced glutathione in their RBCHemoglobin sulfhydryl groups become oxidizedThe hemoglobin precipitates within the RBCforming Heinz bodies.


Defects in the hexose-monophosphate shunt :G6PD DEFICIENCYmost common congenital shunt defectdefective home for the merozoiteover 400 variants of G6PDIn most cases, the alteration is a base substitution, leading to an amino acid replacement DIFERENT SEVERITY:nonspherocytic hemolytic anemia without demonstrable oxidant stress (particularly shortly after birth)through hemolytic anemia only when stimulated by marked to mild oxidant stress, to no clinically detectable abnormality

TYPE B: The normal G6PD TYPE A+: About 20% of individuals of African descent have a G6PD (that differs by a single amino acid and is electrophoretically distinguishable but functionally normal. .type A- : same electrophoretic mobility as the A+ type, but it is unstable and has abnormal kinetic properties 11% of African American malesMediterranean type more severe than the A- Chinesetype : less severe variant


Defects in the hexose-monophosphate shunt :G6PD FICIENCY:sex-linked trait( x linked )

males (hemizygotes)

female carriers (heterozygotes):Lyon hypothesis

Most female carriers are asymptomatic

G6PD activity normally declines ~50% during the 120-day life span of the RBC

A-Varien( mild non clinical anemia )

Stess factor:some type of environmental stress

viral and bacterial infections(most often)mechanism is

unknown

most commonly sulfa drugs, antimalarials, and

nitrofurantoin

Although aspirin is frequently mentioned as a likely offender,

it has no deleterious effect in A- individuals.

Metabolic acidosis , toxic


G6PD FICIENCY :CLINICAL AND LABORATORY FEATURES

acute hemolytic crisis within hours of exposure to the oxidant stressleading to hemoglobinuria and peripheral vascular collapse hemolytic crisis is usually self-limitedSince only the older population of RBC is rapidly destroyedA- variant, the RBC mass decreases by a maximum of 25 to 30%laboratoryHCTrise in plasma hemoglobin unconjugated bilirubin decrease in plasma haptoglobinHeinz bodies, visualized by means of a supravital stain such as crystal violet.Heinz bodies are usually not seen after the first day or so, since these inclusions are readily removed by the spleen "bite cells" (RBC that have lost a peripheral portion of the cell)Multiple bites cause the formation of fragments


Defects in the hexose-monophosphate shunt :G6PD FICIENCY:Mediterranean type G6PD:

much lower overall enzyme activitymore severe clinical manifestationssensitive to fava beans:favism he oxidants in Vicia fava are two b-glycosides whose aglycones, when autooxidized, produce oxygen free radicals.Favism is not encountered in individuals with the A- variant.


Defects in the hexose-monophosphate shunt :G6PD FICIENCYThe diagnosis of G6PD deficiency:

•In any individual, particularly a male of African or Mediterranean descent, who experiences an acute hemolytic episode.

•The enzyme activity or the effects of its deficiency.•A false-negative result during a hemolytic episode when the old RBC containing the defective enzyme have already lysed.


Defects in the hexose-monophosphate shunt :G6PD FICIENCY:TREATMENT:•no specific treatment is necessary.•Since hemolysis in patients deficient in A- G6PD is usually self-limited•Splenectomy does not benefit •Blood transfusions are rarely indicated• Adequate urine flow•Prevention of hemolytic episodes is best•Infections ought to be treated promptly.•warned about risks posed by oxidant drugs and fava beans•Any patient of African or Mediterranean ancestry about to be given an oxidant drug should be screened for G6PD deficiency


Table 108-4. Drugs Causing Hemolysis in Subjects Deficient in G6PD

Antimalarials: Primaquine, pamaquine, dapsoneSulfonamides: SulfamethoxazoleNitrofurantoinAnalgesics: AcetanilidMiscellaneous: Vitamin K (water-soluble form), doxorubicin, methylene blue, nalidixic acid, furazolidone, niridazole, phenazopyridine

ACQUIRED HEMOLYTIC ANEMIAS:

RBC are made normally but are prematurely destroyed because of damage acquired in the circulation.

he exceptions are rare disorders characterized by acquired dysplasia of the cells of the bone marrow

Causes of Acquired Hemolytic Anemia

II. ImmuneA. Warm-reactive (IgG) antibodyB. Cold-reactive IgM antibody (cold agglutinin disease)C. Cold-reactive IgG antibody (paroxysmal cold hemoglobinuria)D. Drug-dependent antibody1. Autoimmune2. HapteneIII. Traumatic hemolytic anemiaA. Impact hemolysisB. Macrovascular defects¾prosthesesC. Microvascular causes1. Thrombotic thrombocytopenic purpura/hemolytic-uremic syndrome2. Other causes of microvascular abnormalities3. Disseminated intravascular hemolysisIV. Hemolytic anemia due to toxic effects on the membraneA. Spur cell anemiaB. External toxins1. Animal or spider bites2. Metals (e.g., copper)3. Organic compoundsV. Paroxysmal nocturnal hemoglobinuria

ACQUIRED HEMOLYTIC ANEMIAS

Hypersplenism

blood circulatingspleenarterioleswhite pulp to sinuses(98%)

red pulpvenous system

1 to 2% "marginal zone" of the lymphatic white pulp cells that occupy this zone are not phagocytic serve as a mechanical filter


Hypersplenism:The normal spleen retains reticulocytes for 1 to 2 days

In infiltrative diseases of the spleen, substantial splenomegaly may exist with no apparent hemolysis; inflammatory and congestive splenomegaly is commonly associated with modest shortening of RBC survival time, along with more marked granulocytopenia and thrombocytopenia.

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of Hemolysis

The Coombs antiglobulin test is the major tool for diagnosing autoimmune hemolysis. neither IgG nor complement may be found on the RBC of the patient (Coombs-negative immune hemolytic anemia)

IgG anti c3 = warm Ab IgM = cold Ab


Table 108-6. Use of the Direct Coombs Test in Diagnosing the Cause of Autoimmune Hemolytic Anemia

Reaction with

Anti-IgG Anti-C3 Causes

Yes No Antibodies to Rh proteins, hemolysis caused by a-methyldopa or penicillin

Yes Yes Antibodies to glycoprotein antigens, SLE

No Yes Cold-reacting antibodies (agglutinins or Donath-Landsteiner antibody), most drug-related antibodies, IgM antibodies, IgG antibodies of low affinity, activation of complement by immune complexes

ACQUIRED HEMOLYTIC ANEMIAS:

Immunologic Causes of Hemolysis

"Warm" antibodies

nearly always IgG occasionally, they are IgA and rarely IgMHemolysis due to autologous antibodies is called autoimmune hemolytic (or immunohemolytic) anemia, warm antibody type

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodies CLINICAL MANIFESTATIONSoccurs at all ages, but it is more common in adults, particularly women.one-fourth an underlying disease: next slide The presentation quite variable

severe anemia [hemoglobin levels 60 to 100 g/L and reticulocyte counts 10 to 30%spherocytosis Splenomegalyfulminant hemolysis associated with hemoglobinemia, hemoglobinuria, and shock; this syndrome may be rapidly fatal unless aggressively treated.The direct Coombs test is positive in 98% of patients

usually IgG is detected with or without C3Evans's syndrome : immune throbocytopenia + anemia Occasionally, venous thrombosis occurs

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisCLINICAL MANIFESTATIONS

Hemolysis due to Antibodies

WARM-ANTIBODY IMMUNOHEMOLYTIC ANEMIA

1. Idiopathic , Lymphomas: Chronic lymphocytic leukemia, non-Hodgkin's lymphomas, Hodgkin's disease (infrequent)

,SLE and other collagen-vascular diseases

Drugs , a-Methyldopa type (autoantibody to Rh antigens) , Penicillin type (stable hapten) Quinidine type (unstable hapten) , Postviral infections Other tumors (rare)COLD-ANTIBODY IMMUNOHEMOLYTIC ANEMIA

cCold agglutinin disease , Acute: Mycoplasma infection, infectious mononucleosis , Chronic: Idiopathic, lymphoma , Paroxysmal cold hemoglobinuria

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodies PATHOGENESIS

IgG antibodies lyse RBC by two mechanisms (1) immune adherence of RBC to phagocytes mediated by the antibody and by complement components that become fixed to the membrane (by far the more important mechanism of destruction), and(2) complement activation. formation of spherocytesIf internalization is only partial, the RBC membrane is removed, resulting in the formation of spherocytes, which are destroyed in the spleen. Complement-mediated immune adherence involves the interaction of C3b and C4b with receptors on the macrophage;

ACQUIRED HEMOLYTIC ANEMIASACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodiesTREATMENT

mild degree of hemolysis usually do not require therapy

clinically significant hemolysis:prednisone, 1.0 mg/kg per day)

A rise in hemoglobin is frequently noted within 3 or 4 days and occurs in most patients within 1 to 2 weeks

Prednisone is continued until the hemoglobin level has risen to normal values, and thereafter it is tapered rapidly to about 20 mg/d, then slowly over the course of several months

For chronic therapy with prednisone, alternate-day administration is preferred


ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodiesTREATMENT

More than 75% initial significant in half these patients the disease recurs, either during glucocorticoid tapering or after its cessation

Glucocorticoids have two modes of action:

an immediate effect due to inhibition of the clearance of IgG-coated RBC by the mononuclear phagocyte system

and a later effect due to inhibition of antibody synthesis.

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodiesTREATMENTimmunosuppressive drugs A success rate of ~50% Intravenous gamma globulin may cause rapid cessation of hemolysisit is not nearly as effective in this disorder as in immune thrombocytopenia.

blood transfusions( problem = selection approprat doner)

antibody in this disease is usually a "panagglutinin," reacting with nearly all normal donor cells, cross-matching is impossible adsorb the panagglutinin present in the patient's serum with the patient's own RBC from which antibody has been previously elutedSerum cleared of autoantibody can then be tested for the presence of alloantibody to donor blood groups

ACQUIRED HEMOLYTIC ANEMIAS: warm antibodyTREATMENT:

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodies

PROGNOSIS:PROGNOSIS:

In most patients, hemolysis is controlled

Fatalities occur among three rare subsets of patients:

(1) those with overwhelming hemolysis who die from anemia;

(2) those whose host defenses are impaired by glucocorticoids, splenectomy, and/or immunosuppressive agents; and

(3) those with major thrombotic events coincident with active hemolysis.

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodiesImmunohemolytic anemia secondary to drugs

two mechanisms of action:

(1) they induce a disorder identical in almost every respect to warm-antibody immunohemolytic anemia (e.g., a-methyldopa )

(2) they become associated as haptenes with the RBC surface and induce the formation of an antibody directed against the RBC-drug complex (e.g., penicillin, quinidine).

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodies : druges

a-methyldopa therapy in doses of 2 g/d or higherA positive direct Coombs test up to 10% a-Methyldopa alters and makes immunogenic the protein(s) of the Rh complexthe resulting antibodies cross-react with the normal Rh protein. Thus the antibody does not react with the drugand the indirect Coombs test is positive in almost all patients even when the drug is not added to the test.The RBC are coated with IgG but not C3Hemolysis decreases over the course of several weeks after cessation of drug therapy, although the direct Coombs test may remain positive for more than 1 year

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisWarm" antibodies : druges

In most other cases of drug-induced hemolysis, the antibody is directed against the combination of the drug and the membrane glycoprotein to which it is attached.

he hemolytic reaction in vivo is dependent on the presence of the drug and usually ceases shortly after the drug has been discontinued

Penicillin and its congeners may cause this type of reaction if the drug is given in very high doses (10 million units per day or more)

Complement is not usually fixed, and the hemolysis in vivo is usually not severe.

Since the antibody is usually IgG, spherocytosis and splenic destruction may occur


Warm" antibodies : druges

Most other drugs (such as quinine, quinidine, sulfonamides, sulfonureas, phenacetin, stibophen, and dipyrone) do not adhere as tightly to their glycoproteins, and the drug-antibody complexes are removed during the washing steps of the direct and indirect Coombs reactions.

These antibodies (particularly IgM) are usually able to fix complement, and these components remain on the RBC surface; thus the direct Coombs test is positive with anti-C3 but not anti-IgG. The antibody is detected in the indirect Coombs test only when the drug is added to the incubation mixture

Hemolysis may be quite severe, sometimes resulting in signs of intravascular hemolysis; resolution is usually prompt after the drug is discontinued.


Immune hemolysis due to cold-reactive antibodies :

Antibodies that react with polysaccharide antigens are usually IgM and

react better at temperatures lower than 37°C

Uncommonly, the antibody is IgG (the Donath-Landsteiner antibody of paroxysmal cold hemoglobinuria)

Cold agglutinins arise in two clinical settings:

(1) monoclonal antibodies, the product of lymphocytic neoplasia or paraneoplasia, and (2) polyclonal antibodies in response to infection.

In many elderly patients, the "neoplasm" is benign monoclonal gammopathy that does not progress, and the paraprotein remains its only manifestation


Immune hemolysis due to cold-reactive antibodies

• Occasionally, cold agglutinins are found in patients with

nonlymphoid neoplasms.

•Transient cold agglutinins occur commonly in two infections:

Mycoplasma pneumoniae infection and infectious

mononucleosis. ]

•in both, the titer of antibody is usually too low to cause clinical

symptoms, but its presence is of diagnostic value

•other viral infections.



Cold agglutinins reacting more strongly with adult RBC than fetal (cord) RBC are called anti-Ithese antibodies are seen in benign lymphoproliferation (chronic cold agglutinin monoclonal gammopathy) and in Mycoplasma infections

Those reacting more strongly with cord RBC cells are called anti-I these antibodies are seen in aggressive lymphomas and in infectious mononucleosis

the clinical manifestations elicited by the antibody on exposure to cold two :

1. intravascular agglutination (acrocyanosis)

2. H emolysis



acrocyanosis:

Acrocyanosis is the marked purpling of the extremities, ears, and nose when the blood becomes cold enough to agglutinate in the veins; it clears on warming and does not have the vasospastic characteristics of Raynaud's phenomenon

Patients may also have symptoms when swallowing cold food or drinks.

Hemolysis

is usually not severe and is manifested by a mild reticulocytosis, agglutination on the blood film, and agglutination during analysis of the blood by particle analysis (giving rise to a falsely high mean corpuscular volume). The degree of hemolysis depends on several variables: next slid



Variable of hemolysis

1. Antibody titer. in symptomatic patients is above 1:2000 dilution of serum and may range to as high as 1:50,000

2. Thermal amplitude of the antibody (the highest temperature at which the antibody will react with the RBC)

For most antibodies, this is 23 to 30°C

3. Environmental temperature

The hemolysis that occurs is due primarily to the hemolytic action of complement, since there are no functional Fc receptors for the IgM antibody

the normal human RBC is remarkably resistant to the hemolytic action of complement because of several defense mechanisms.

severe hemolysis with hemoglobinuria occurs only with massive activation of the antibody, such as by sudden cooling



The activation of complement is always marked by the accumulation of a degradation product of C3, C3dg, on the surface; this product is what is detected with appropriate antisera in the direct Coombs test in all patients with significant cold agglutinin diseas

The cutaneous manifestations and hemolysis are best treated by maintaining the patient in a warm environment.Splenectomy is usually not of value in this disorderGlucocorticoids are of limited value

although patients with the panthermal variety of cold agglutinin disease may respond

Chlorambucil and cyclophosphamide are commonly used to treat patients who have hemolysis associated with monoclonal gammopathy, but their efficacy is usually marginal

Successful treatment of the malignant neoplasm responsible for the cold agglutinin often reduces the titer of antibody and the severity of the hemolysis.

ACQUIRED HEMOLYTIC ANEMIAS:Immunologic Causes of HemolysisImmune hemolysis due to cold-reactive antibodies

Paroxysmal cold hemoglobinuria (PCH)Now a rare disorderPCH was more frequent when tertiary syphilis was prevalentnow, most cases are either secondary to a viral infection or areautoimmune.

PCH results from the formation of the Donath-Landsteiner antibody, an IgG antibody that is directed against the P antigen can induce complement-mediated lysis

Attacks are precipitated by exposure to cold and are associated with hemoglobinemia and hemoglobinuria; chills and fever; back, leg, and abdominal pain; headache; and malaise

Recovery from the acute episode is prompt, and between episodes patients are usually asymptomatic.

When this syndrome accompanies acute viral infections (e.g., measles and mumps in children), it is self-limited but may be severe


Immune hemolysis due to cold-reactive antibodiesParoxysmal cold hemoglobinuria (PCH)

Although the direct Coombs test may show complement to be present (seldom IgG), this test may be negative

The diagnosis is made by demonstrating cold-reacting IgG antibodies either by lytic tests (when the titer is very high) or by special antiglobulin tests

When PCH is secondary to syphilis, it responds to therapy for syphilis.

Chronic autoimmune PCH may respond to prednisone or cytotoxic therapy (azathioprine or cyclophosphamide) but does not respond to splenectomy

Hemolysis due to Trauma in the CirculationRBC fragments called schistocytesin three clinical settings:(1) External impact (2) Macrovascular (3) Microvascular

Changes in RBC and Platelets Induced by Intravascular TraumaEtiology Fragment

sHemolysis

Thrombocytopenia

Impact: march hemoglobinuria, etc.

0 + 0

Cardiac (turbulence):

Aortic valve prosthesis ++++ ++++ 0

Mitral valve prosthesis ++ ++ 0

Calcific aortic stenoses + ± 0

Vessel diseasea +++ + +

Thrombotic thrombocytopenic purpura

++++ ++++ ++++

Hemolytic-uremic syndrome ++++ ++++ ++++

Adenocarcinoma ++++ ++++ ++++

Disseminated intravascular coagulation

++ ± ++++

a Malignant hypertension, eclampsia, renal graft rejection, hemangiomas, immune disease (scleroderma).

Hemolysis due to Trauma in the CirculationExternal impact

Hemoglobinemia and hemoglobinuria

prolonged march or a prolonged run

hemolysis can be prevented by the insertion of a soft inner sole

in the runner's shoes

may produce myoglobinuria

renal function is preserved

No specific therapy is required except to obtain better running

shoes.

•Hemolysis due to Trauma in the Circulation•Macrovascular traumatic hemolysis •10% of patients with artificial aortic valve prostheses.

•greater with valves having stellite rather than Silastic occluders, greater with small valves as compared with larger valves, and greater when valves are cloth-covered or when there is a paravalvular leak•Traumatic hemolysis is rare in recipients of porcine valves

•ostium primum or endocardial cushion defects with a prosthetic patch•Mitral valve prostheses incidence is lower• severe calcific aortic stenosis• aortofemoral bypass•CLINICAL MANIFESTATIONS•Anemia :50 to 70 g/L reticulocytosis fragmented RBC depressed haptoglobin elevated serum LDH hemoglobinemia hemoglobinuria iron dif. Anemia The direct Coombs test may rarely become positive.

•Hemolysis due to Trauma in the Circulation•Macrovascular traumatic hemolysis •PATHOGENESIS•(1) the shear stress•(2) direct mechanical trauma•3) the deposition of fibrin •TREATMENT•Iron deficiency•Limitation in physical activity•any paravalvular leak must be repaired or the prosthetic valve replaced.

Hemolysis due to Trauma in the CirculationMicrovascular traumatic hemolysis

fibrin or platelet microthrombi are deposited in arteriolar sites fibrin or platelet microthrombi are deposited in arteriolar sitesmalignant hypertension, eclampsia, renal allograft rejection, disseminated cancer, hemangiomas, or disseminated intravascular coagulation (DIC) The degree of hemolysis induced by this family of disorders is usually quite mildThrobocytopenia may be

Hemolysis due to Trauma in the CirculationMicrovascular traumatic hemolysis Thrombotic thrombocytopenia purpura (TTP)

Arteriolar lesions in various organs that contain platelet thrombi Primarily young adults and more often women.CLINICAL MANIFESTATIONS

intravascular hemolysis, thrombocytopenia, diffuse and nonfocal neurologic findings, decreased renal function, and fever

The neurologic and renal symptoms are usually seen only when the platelet count is markedly diminished (<20 to 30 ´ 103/uL)

Thrombocytopenia often parallels anemia

Fever is not reliably present

TTP may be acute in onset, but its course spans days to weeks in most patients and occasionally continues for months

Neurologic symptoms

develop in >90% of patients whose disease terminates in death

mental status such as confusion, delirium, or altered states of consciousness may occur. Focal findings include seizures, hemiparesis, aphasia, and visual field defects. These neurologic symptoms may fluctuate and terminate in coma

Hemolysis due to Trauma in the Circulation

Microvascular traumatic hemolysis Thrombotic thrombocytopenia purpura (TTP)CLINICAL MANIFESTATIONS

myocardial blood vessels

The severity of the disorder can be estimated from the degree of anemia and thrombocytopenia and the serum LDH level

The severity of the disorder can be estimated from the degree of anemia and thrombocytopenia and the serum LDH level

If the coagulation tests indicate a major consumption of clotting factors, the diagnosis of TTP is doubtful

A positive antinuclear antibody (ANA) determination is obtained in approximately 20% of patients.

Hemolysis due to Trauma in the CirculationMicrovascular traumatic hemolysis Thrombotic thrombocytopenia purpura (TTP)

DIAGNOSIS:

Although they are not usually required for diagnosis, biopsies of skin and muscle, gingiva, lymph node, or bone marrow may show the typical arteriolar abnormalities. The combination of hemolytic anemia with fragmented RBC, thrombocytopenia, normal coagulation tests, fever, neurologic disorders, and renal dysfunction is virtually pathognomonic of TTP

hemolysis: premature destruction of the red cells

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