Basic Introduction ANEMIA and RBCs Physiology

Basic Introduction ANEMIA and RBCs

Physiology

Physiology

-Proliferation and differentiation of red cell precursors is stimulated by erythropoietin (EPO), a polypeptide hormone produced by renal interstitial peritubular cells in response to hypoxia. -Normal mature red cells circulate for about 120 days **Increased numbers of circulating reticulocytes (reticulocytosis) “Polychromasia” reflect increased erythropoiesis RI = reticulocyte % × actual Hct/normal Hct Measures appropriate bone marrow response to anemic conditions (effective erythropoiesis). High reticulocyte index (RI) indicates compensatory RBC production; low RI indicates inadequate response to correct anemia.

EPO from the kidneys*

Hemoglobin

A protein specially adapted for oxygen transport. It is composed of four globin chains, each surrounding an iron-containing (ferrous ion (Fe2+) porphyrin pigment molecule termed heme.

Globin chains are a combination of two alpha and two non-alpha chains;

HbA (αα/ββ) >90% of adult hemoglobin

HbF (αα/γγ) fetus

HbA2 (α2δ2) <3.1%

Alpha globin chains are produced by two genes on chromosome 16, and beta globin chains by a single gene on chromosome 11.

Imbalance in the production of globin chains results in the thalassaemias

Definition

Anaemia refers to a state in which haemoglobin in the blood is below the reference range appropriate for age and sex. Other factors like pregnancy and altitude must be taken into consideration..

World Health Organization (WHO) defines anemia (at sea level) as:

Hb < 13 g/dL (130 g/L) in men ≥ 15 years old

Hb < 12 g/dL (120 g/L) in nonpregnant women ≥ 15 years old or adolescents aged 12-14 years

Causes

Decrease or ineffective marrow production Lack of iron, folic acid or vit. B12. Myelodysplasia Invasion of malignant cells Renal failure Anaemia of chronic disease Normal production but increased removal of cells Blood loss Haemolysis & survival defect Hypersplenism (Sequestration)

Evaluation

Patients may be asymptomatic due to development of anemia over weeks or months, allowing the body to compensate for lower oxygen carrying capacity.

There is no specific Hb concentration that leads to development of symptoms, but most patients will present with symptoms when Hb drops to < 7 g/dL (70 g/L). However, patients with conditions of limited cardiac function (for example, heart failure or coronary artery disease) may present with symptoms of anemia at a higher Hb level than those with normal cardiac function.

Symptoms and signs Clinical Presentation.

. Early symptoms include fatigue, tiredness, and poor exercise tolerance.

As the anemia worsens, the patient develops dyspnea on exertion and lightheadedness.

Eventually, confusion and altered mental status may develop as oxygen delivery to the brain decreases.

Death from anemia is most often from decreased oxygen delivery to the heart, resulting in the development of myocardial ischemia

Signs -

mucous membrane pallor, tachypnoea, tachycardia, flow murmurs, ankle edema, postural hypotension., jaundice, scleral icterus, dark urine, hepatosplenomegaly, splenic fullness, and in severe cases, angina, fever, pallor, signs of heart failure, and hemoglobinuria

Physical exam must asses vital signs and the site and severity of bleeding

*May be disease specific

Diagnosis.

Once a diagnosis of anemia is determined based on a low hematocrit or hemoglobin, the first step is to determine the MCV.

Iron studies, reticulocyte count, peripheral smear, red cell distribution width (RDW), Coombs test, vitamin B12, folate levels, and a bone marrow biopsy may be necessary to determine a specific etiology. The tests ordered depend on the specifics of the case presented

Reticulocyte index

Reports the number of reticulocytes present as a percentage of the total number of RBCs.

The reticulocyte count is an important initial test in evaluating anemia because it indicates whether effective erythropoiesis is occurring in the bone marrow

Effective erythropoiesis is dependent on adequate raw materials (iron, vitamin B12 , folate) in the bone marrow, absence of intrinsic bone marrow disease (e.g., aplastic anemia), adequate erythropoietin from the kidney, and survival of reticulocytes (no premature destruction before leaving the bone marrow)

A reticulocyte index >2% implies the bone marrow is responding to increased RBC requirementse

. A reticulocyte index <2% implies inadequate RBC production by the bone marrow

Initial management is dependent on patient clinical status: Patients who are bleeding: Control bleeding. This may involve surgery, gastroenterology, or involvement of specialist such as interventional radiology. In patients with hemodynamic instability, ongoing bleeding, or tissue hypoxia, transfuse RBCs (Strong recommendation).

Patients who are hemodynamically stable: Not all patients require immediate management. Indications for transfusion (excluding those with acute coronary syndrome, severe thrombocytopenia [patients with hematological or oncological conditions at risk of bleeding], and those with chronic transfusion-dependent anemia):

Transfusion is not indicated until Hb level drops to 7 g/dL (70 g/L) or less

Managment

Microcytic and Normocytic Anemia

Diagnosing the cause of anemia

If microcytic anemia (MCV<80), the differential diagnosis includes the following:

•Iron deficiency anemia —most common cause

•Anemia of chronic disease —iron is present in the body but is not available for hemoglobin synthesis (iron trapping in macrophages)

•Thalassemias —defective synthesis of globin chains

•Ring sideroblastic anemias (includes lead poisoning, pyridoxine deficiency, toxic effects of alcohol)—this is a defective synthesis of

protoporphyrins. Iron accumulates in mitochondria

If normocytic anemia, the differential diagnosis includes the following:

Aplastic anemia

Bone marrow fibrosis

Tumor

Anemia of chronic disease (chronic inflammation, malignancy)

Renal failure (decreased erythropoietin production)

Microcytic Anemias Iron Deficiency Anemia

Most common cause of anemia worldwide

Causes

Chronic blood loss

Most common cause of iron deficiency anemia in adults

Menstrual blood loss is the most common source. In the absence of menstrual bleeding, GI blood loss is most likely In elderly patients with iron deficiency anemia, you must rule out colon cancer

Malabsorption

Gastric acid is required to release iron from food and helps to keep iron in the soluble ferrous state.

Achlorhydria in the elderly or that due to drugs such as proton pump inhibitors may contribute to the lack of iron availability from the diet, as may previous gastric surgery.

Iron is absorbed actively in the upper small intestine and hence can be affected by coeliac disease

Dietary deficiency/increased iron requirements—primarily seen in these three age groups:

Infants and toddlers—occurs especially if the diet is predominantly human milk (low in iron). Children in this age group also have an increased requirement for iron because of accelerated growth. It is most common between 6 months and 3 years of age

Adolescents—rapid growth increases iron requirements. Adolescent women are particularly at risk due to loss of menstrual blood

Pregnant women—Pregnancy increases iron requirements

Iron Deficiency Anemia Presentation

Clinical features

Fatigue, generalized weakness

Dyspnea on exertion

Orthostatic lightheadedness

Physical Examination

Hypotension, if acute

Tachycardia

Pallor

Iron Deficiency Anemia Diagnosis

1) Laboratory tests

Decreased serum ferritin—most reliable test available.

Increased TIBC/transferrin levels

Low TIBC saturation

Decreased serum iron

2) Peripheral Smear: Microcytic, hypochromic RBCs

but rarely performed. Indicated if the gold standard, —) Bone marrow biopsy3laboratory evidence of iron deficiency anemia is present and no source of blood loss is found

4) If GI bleeding is suspected—guaiac stool test or colonoscopy. Colon cancer is a common cause of GI bleeding in the elderly

Iron Deficiency Anemia Treatment Oral iron replacement (ferrous sulfate).

A trial should be given to a menstruating woman. However, in men and post-menopausal women with iron deficiency anemia, attempt to determine the source of blood loss.

Side effects include constipation, nausea, and dyspepsia.

200 mg 3 times daily (195 mg of elemental iron per day) is adequate and should be continued for 3–6 months to replete iron stores.

Delayed-release preparations are not useful, since they release iron beyond the upper small intestine, where it cannot be absorbed

The hemoglobin should rise by around 10 g/L every 7–10 days and a reticulocyte response will be evident within a week.

A failure to respond adequately may be due to non-adherence, continued blood loss, malabsorption or an incorrect diagnosis.

2) Parenteral iron replacement.

Iron dextran can be administered IV or IM.

This is rarely necessary because most patients respond to oral iron poor absorption, patients therapy. It may be useful in patients with

who require more iron than oral therapy can provide, or patients who cannot tolerate oral ferrous sulfate.

3) Blood transfusion is not recommended unless anemia is severe or the patient has cardiopulmonary disease

Thalassemias

General characteristics

Inherited disorders characterized by inadequate production of either the

α- or β-globin chain of hemoglobin

They are classified according to the chain that is deficient

β-Thalassemias.

β-chain production is deficient, but the synthesis of α-chains is unaffected

Excess α-chains bind to and damage the RBC membrane

It is most often found in people of Mediterranean, Middle Eastern, and Indian ancestry

Severity varies with different mutations.

α-Thalassemias.

There is a decrease in α-chains, which are a component of all types of hemoglobins

The β-globin chains form tetramers, which are abnormal hemoglobin

The severity depends on the number of gene loci that are deleted/mutated—it ranges from an asymptomatic carrier state to prenatal death

b-Thalassemias

1.Thalassemia major (Cooley anemia; homozygous β-chain thalassemia)—occurs predominantly in Mediterranean populations

Clinical features

Usually diagnosed between 6 and 12 months of age

• Severe anemia (microcytic hypochromic)

• Massive hepatosplenomegaly

• Expansion of marrow space—can cause distortion of bones

• Growth retardation and failure to thrive

• Skull x-ray may show “crew-cut” appearance

• If untreated (with blood transfusions),death occurs within the

first few years of life secondary to progressive CHF

Diagnosis

• Hemoglobin electrophoresis—Hb F and Hb A2 are elevated

• Peripheral blood smear—microcytic hypochromic anemia, target cells may be seen (Figure 9-3)

Treatment —frequent PRBC transfusions are required to sustain life. , Patients are entirely transfusion dependent. Iron overload can develop in patients with transfusion-dependent thalassemia. If untreated, this can lead to CHF and other symptoms of hemochromatosis. These individuals are often treated with deferoxamine, an ironchelating agent.

2.Thalassemia minor (heterozygous β-chain thalassemia)

Clinical features: patients are usually asymptomatic. A mild microcytic, hypochromic anemia is the only symptom.

Diagnosis: hemoglobin electrophoresis

Treatment: usually not necessary (Patients are not transfusion dependent.)

3.Thalassemia intermedia

a. Usually involves both β-globin genes

b. Severity of anemia is intermediate

c. Patients usually are not transfusion dependent

a-Thalassemias

1.Silent carriers—mutation/deletion of only one α-locus.

•Asymptomatic

•Normal hemoglobin and hematocrit level

•No treatment necessary

2.α-Thalassemia trait (or minor)—mutation/deletion of two α-loci.

•Characterized by mild microcytic hypochromic anemia

•Common in African-American patients

•No treatment necessary

3.Hb H disease—mutation/deletion of three α-locia.

Hemolytic anemia, splenomegaly

Significant microcytic, hypochromic anemia

Hemoglobin electrophoresis shows Hb H

Treatment is often the same as for patients with β-thalassemia major. Splenectomy is sometimes helpful

4.Mutation/deletion of all four α-loci

This is either fatal at birth (hydrops fetalis (

or shortly after birth

Sideroblastic Anemia

Caused by abnormality in RBC iron metabolism. Hereditary or acquired

Acquired causes include drugs (chloramphenicol,INH,alcohol), exposure to lead, collagen vascular disease, and neoplastic disease (myelodysplastic syndromes).

Clinical findings: increased serum iron and ferritin, normal TIBC, TIBC saturation is normal/elevated, which distinguishes it from iron deficiency; ringed sideroblasts in bone marrow.

Treatment: remove offending agents. Consider pyridoxine

Normocytic Anemias 1- Anemia of Chronic Disease

Occurs in the setting of chronic infection (e.g.,tuberculosis, lung abscess)

Cancer (e.g., lung, breast, Hodgkin disease)

Inflammation (rheumatoid arthritis, systemic lupus erythematosus [SLE])

Trauma.

The release of inflammatory cytokines has a suppressive effect on erythropoiesis.

It may be difficult to differentiate from iron deficiency anemia.

Laboratory findings: low serum iron, low TIBC, and low serum transferrin levels occur. Serum ferritin levels are increased. The anemia is usually normocytic and normochromic, but may be microcytic and hypochromic as well.

No specific treatment is necessary other than treatment of the underlying process. Do not give iron. The anemia is usually mild and well tolerated. A trial of oral iron can be given in difficult situations. A positive response occurs in true iron deficiency but not in ACD.

Anemia of Chronic Disease Pathogenesis It has recently become clear that the key regulatory protein that accounts for the findings characteristic of ACD/AI is hepcidin, which is produced by the liver Hepcidin production is induced by pro-inflammatory cytokines, especially IL-6.

Hepcidin binds to ferroportin on the membrane of iron-exporting cells, such as small intestinal enterocytes and macrophages, internalizing the ferroportin and thereby inhibiting the export of iron from these cells into the blood.

The iron remains trapped inside the cells in the form of ferritin, levels of which are therefore normal or high in the face of significant anemia.

Inhibition or blockade of hepcidin is a potential target for treatment of this form of anemia.

Aplastic Anemia Bone marrow failure leading to pancytopenia (anemia, neutropenia, thrombocytopenia)

Causes

Idiopathic—majority of cases

Radiation exposure

Medications (e.g., chloramphenicol, sulfonamides, gold, carbamazepine)

Viral infection (e.g., human parvovirus, hepatitis C, hepatitis B, Epstein–Barr virus (EBV), cytomegalovirus, herpes zoster varicella, HIV)

Chemicals (e.g., benzene, insecticides)

Clinical features

Symptoms of anemia—fatigue, dyspnea

Signs and symptoms of thrombocytopenia (e.g., petechiae, easy bruising)

Increased incidence of infections (due to neutropenia)

Can transform into acute leukemia

Diagnosis

1. Normocytic, normochromic anemia.

2. Perform a bone marrow biopsy for definitive diagnosis—this reveals hypocellular marrow and the absence of progenitors of all three hematopoietic cell lines.

Treatment

1.Bone marrow transplantation

2.Transfusion of PRBCs and platelets, if necessary (use judiciously)

3.Treat any known underlying causes

Macrocytic Anemia: (MCV>100).

Deferential diagnosis:

- Nuclear defects(MCV increases significantly): Vitamin B12/Folate deficiency. (megaloblastic Anemia).

- Liver disease: (MCV increases up to 115): altered metabolism of lipoproteins in cell membranes = altered RBC shape.

- Alcoholism.

- Stimulated erythropoiesis: reticulocytes are larger than RBCs, resulting in an increase in polychromatophilic RBCs.

Vitamin B12 deficiency : General Characteristics Vitamin B 12 serves as a cofactor in two important reactions required for normal erythropoiesis and CNS functioning A. The conversion of homocysteine to methionine b. The conversion of methylmalonyl-CoA to succinyl-CoA

Vitamin B12 is found in animals products like meat, fish and milk…

Bound and absorbed with the Intrinsic factor at the level of ilium.

Causes of deficiency (mostly due to impaired absorption):

-Pernicious anemia (Lack of intrinsic factor): most common cause in the western hemisphere. -Gastrectomy: B12 needs low PH environment to be released from food.

-Poor Diet: (e.g. strict vegetarian).

-Alcohol: prevent absorption.

-crohn disease/ileal resection(the last 100cm).

-Some organism the compete with b12: fish tapeworm(Diphyllobothrium latum)/bacterial overgrowth.

Clinical features:

Anemia symptoms: pallor, headache, malaise, shortness of breath, fatigue, poor concentration, confusion, nausea, vague, hypotension, tachycardia.

Sore tongue: Stomatitis and glossitis.

Neuropathy vit b 12 is important in myelination prolong vitb12 deficiency lead to subacute combined degeneration SCD :: Can distinguish between vitamin B12 and folate deficiency: Spinal cord demyelination: loss of position/vibration sensation in lower extremities, Ataxia, upper motor neuron signs (increased deep tendon reflex,weakness, spasticity, Babinski sign).

Can lead to urinary and fecal incontinence, impotence

Diagnosis:liver stores in a healthy person 2-3 years worth of vitamin b 12 -CBC: low hemoglobin/MCV : high.

-Peripheral blood smear: macrocytic RBCs, hyper-segmented neutrophils.

-Serum vitamin B12 level is low (<200 pg/ml).

-Serum mythelmalonic acid and homocysteine levels – MMA is elevated in B12 deficiency not folate.

-Antibodies against intrinsic factor for diagnosis of pernicious anemia.

Treatment: Daily injections for 1 week, then weekly injections for 1 month, then monthly.

Folate Deficiency:

Folic acid stores and limited. Inadequate intake of folate over a 3-month period can lead to deficiency.

Found in green vegetables as the main source, but over cooking it remove the folate.

Causes:

-Inadequate dietary intake such as “tea and toast”

(Tea and toast syndrome is a form of malnutrition commonly experienced by elderly people who are unable to prepare meals and tend to themselves. Their diets often dwindle to tea and toast resulting in a deficiency of vitamins and other nutrients).

-Alcoholism.

-long term use of oral antibiotics.

-increased demand: pregnancy.

-use of folate antagonist such as methotrexate.

-anticonvulsant medication: phenytoin.

- Sulfa drugs in HIV pt for prophylactics

-hemodialysis.

--Clinical features are same as B12 deficiency anemia except there are no neurological symptoms.

Treatment: daily oral supplements of folic acid.-

• Hemolytic anemia general principles

• SICKLE CELL DISEASE

• AUTOIMMUNE, COLD AGGLUTININ, AND DRUG-INDUCED HEMOLYTIC ANEMIA

• HEREDITARY SPHEROCYTOSIS

• PAROXYSMAL NOCTURNAL HEMOGLOBINURIA

• GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY

• Hemolytic anemias are caused by decreased RBC survival from increased destruction of the cells.

• Chronic vs. acute

• Extravascular vs. Intravascular

• Clinical Presentation :

- The usual symptoms of anemia (Fatigue and weakness occur with mild disease , Dyspnea and later confusion )

- Usually the onset is sudden . “simple blood loss excluded”

- Associated with jaundice and dark urine

- Fever, chills, chest pain, tachycardia, and backache may occur if the intravascular hemolysis is particularly rapid.

• Diagnosis:

• Normal MCV , The reticulocyte count is elevated (10–20% range),

• The LDH and indirect bilirubin are elevated .

• peripheral smear abnormalities

• haptoglobin maybe low with intravascular hemolysis

• Hemoglobin and Hemosiderin , Hemosiderin may be present in the urine

• There should not be bilirubin in the urine

• Treatment. Transfusion is needed as in all forms of anemia when the hematocrit becomes low. Hydration is, in general, useful to help prevent toxicity to the kidney tubule from the free hemoglobin

SICKLE CELL DISEASE

• Pathology : Autosomal recessive hereditary disease

• Hemoglobin S is due to a substitution of a valine for glutamic acid as the sixth amino acid of the beta globin chain .

• Heterozygous form vs. Homorozygous form

• A sickle cell acute painful crisis may be precipitated by hypoxia, dehydration, acidosis, infection, and fever.

• Sickle cell crisis is usually not associated with an increase in hemolysis or drop in hematocrit.

• Clinical Presentation :

• chronic : renal concentrating Defects, hematuria, bilirubin, Gallstones, osteomyelitis, retinopathy, recurrent infections from Pneumococcus or Haemophilus , splenomegaly (autosplenectomy)

• Acute painful crisis : PAIN, • life-threatening manifestations of sickling :

1) acute chest syndrome : (severe chest pain, fever, leukocytosis, hypoxia, and infiltrates on the chest x-ray. )

2) Stroke and TIA

3) Priapism

4) Blindness , myocardial infarction and cardiomyopathy

5) spontaneous abortion and low birth weight

Sickle trait gives normal hematologic picture with no anemia and a normal MCV.

The only significant manifestation of trait is the renal concentrating defect presenting with isosthenuria and microscopic hematuria

Increase risk for UTIs .

• Diagnosis:

• mild to moderate anemia.

• The hemoglobin electrophoresis is the most specific test.

• The peripheral smear shows sickled cells.

• The sickle prep

• The white blood cell count is often elevated in the 10,000–20,000 range.

• Treatment:

• An acute sickle cell pain crisis is treated with fluids, analgesics, and oxygen.

• Antibiotics(Ceftriaxone) are given with infection or even to patients with fever and leukocytosis.

• In life threatening conditions : are managed with red blood cell transfusions if the hematocrit is low, and exchange transfusion if the hematocrit is high

• Chronic management:

• folic acid replacement and vaccinations

• Hydroxyurea

• Bone marrow transplantation

AUTOIMMUNE, COLD AGGLUTININ, AND DRUG-INDUCED HEMOLYTIC ANEMIA • can result from the production of IgG, IgM, or activation of

complement C3 against the red cell membrane

• Cold ass. With IgM Vs. Warm ass. With IgG

• Cause usually idopathic

• Chronic deseases/drugs could induce it

• The most common drugs are the penicillins, cephalosporins, sulfa drugs, quinidine, alphamethyldopa, procainamide, rifampin, and thiazides.

• Clinical Presentation :

• The onset may be very sudden resulting in fever, syncope, congestive failure, and hemoglobinuria

• Mild splenomegaly ( long duration )

• Cold agglutinin disease : cyanosis of the ears, nose, fingers, and toes.

• Diagnosis :

• The Coombs test is the specific test that diagnoses autoimmune

• Spherocytes are often present on the smear

HEREDITARY SPHEROCYTOSIS

• Pathology : autosomal dominant disorder where the loss of spectrin in the red cell membrane

• Clinical Presentation :

• A chronic disorder with mild to moderate symptoms of anemia.

• there is often splenomegaly and jaundice.

• Diagnosis:

• osmotic fragility test.

• The mean corpuscular hemoglobin concentration (MCHC) is elevated.

• a negative Coombs test.

• Treatment:

• Most patients require no treatment beyond folate replacement chronically.

• more severe anemia : spleen removal

PAROXYSMAL NOCTURNAL HEMOGLOBINURIA • Pathology : A red cell membrane defect in phosphatidyl-inositol glycan A (PIGA)

allows increased binding of complement to the red cell, leading to increased intravascular hemolysis.

• Clinical Presentation:

• Thrombosis of major venous structures, particularly the hepatic vein is a common cause of death in these patients

• Diagnosis : The gold standard test is flow cytometry for CD55 and CD59 on white and red cells. In PNH, levels are low or absent.

Treatment. • Some patients with few or no symptoms require only folic acid and possible

iron supplementation.

• The disease may progress : • prednisone is often given to slow the rate of red blood cell destruction. • In the patient with acute thrombosis, thrombolytic therapy (streptokinase) • Antiplatelet agents and avoid medication that increase the risk for

thrombosis (OCPs) • Allogeneic bone marrow transplantation has been the mainstay of curative

therapy for PNH

• Eculizumab treat the symptoms

GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY • Pathology : X-linked recessive , G6PD defect leads to increase RBCs

susceptibility to oxidative stress .

• The most common type of oxidant stress is actually from infections, not drugs.

• The most commonly implicated drugs are sulfa drugs, primaquine, dapsone, quinidine, and nitrofurantoin.

Clinical Presentation :

• A sudden, severe, intravascular hemolysis, jaundice, dark urine, weakness, and tachycardia.

• The main clue : history of recent drug ingestion

• Diagnosis:

• Heinz bodies, Bite cells are seen on smear.

• The definitive test is the G6PD level, which can be falsely normal immediately after an episode of hemolysis. Hence, the level is best tested about 1 week after the event.

• Treatment:

• There is no specific therapy beyond hydration and transfusion if the hemolysis is severe.

• The main therapy is to avoid oxidant stress in the future.