Disorders Of The Rbc

Hematopoiesis

• Term used to describe the normal formation

of blood cells in the bone marrow.

Bone

Marrow

• Produces all the hematopoietic cells in

adults. • Present in all bone marrow cavities at birth and early childhood • By age 20 – 25 years, red marrow is present in cranial bones, vertebrae, sternum, ribs, clavicle, scapula, pelvis, proximal end of the femur and humerus.

Process

of RBC formation Substances needed for erythropoiesis: • Iron • Vitamin B12 • Copper and Cobalt • Folic Acid • Pyridoxine (vitamin B6)

Aging or abnormal erythrocytes Lysed by the liver and spleen

•Iron is recycled by transferrin •Heme molecule is converted to unconjugated bilirubin Conjugated with protein in the liver

Urine: urobilinogen

GIT: Bile

Excreted

Blood

are classified into different groups and typed according to antigens present on the red cell membrane

 Rh

type is determined by the presence or absence of the Rhesus factor.  Unlike the ABO antigens, the only ways antibodies are developed against the Rh factor are through placental sensitization or transfusion  85% of whites and 95% of African Americans in the US are Rh+  Incompatibility happens when the mother is Rh- and the baby is Rh+

A

group of condition characterized by an increase in the hematocrit.

Problem:

increases.

viscosity of the blood

Causes:

• Hypoxemia High altitutes Chronic pulmonary diseases • Overproduction of erythropoietin Renal diseases Malignant tumors Disturbance of renal blood flow

Characterized

by normal erythrocyte count and a reduced plasma volume. Cause: dehydration

Myeloproliferative

disorder in which there is an increase production of all the formed elements of blood.

Abnormally

low number of circulating

RBCs or hemoglobin level, or both, resulting in diminished oxygencarrying capacity. Most

common hematologic condition

Causative

factors:

• Excessive loss of RBCs • Excessive destruction • Deficient RBC production • Bone marrow failure

•

Signs and symptoms caused by tissue hypoxia. Angina, night cramps, fatigue, weakness, and dyspnea

• • • • • •

Brain hypoxia: headache, faintness, and dim vision. Pallor of the skin, mucous membranes, conjunctiva, and nailbeds. Tachycardia and palpitations Diffuse bone pain and sternal tenderness. Jaundice (in hemolytic anemia) Petechiae and purpura (in aplastic anemia)

 Bleeding

 iron and other components of the erythrocytes are lost from the body.  May be acute or chronic  RBC concentration returns to normal within 3 – 4 weeks if the bleeding is controlled and when sufficient iron stores are available.  Patients are commonly asymptomatic until the hemoglobin level is less than 8 g/dL.

Characterized

by the premature destruction of RBCs RBCs have shortened lifespan Bone marrow is usually hyperactive

A.

RED CELL MEMBRANE DEFECTS 1. Hereditary Spherocytosis 2. Acquired Immune Hemolytic anemia 3. Hemolytic Blood Transfusion Reactions

A

group of inherited hemolytic anemias that are mainly due to inherited autosomal dominant conditions that result in a molecular defect of the RBC membrane.  Characteristic: • RBCs are spherical in shape and are

prematurely destroyed in the spleen.

 Manifestations:

• Jaundice • Splenomegaly • Signs of anemia

Result

from premature destruction of the RBCs by autoantibodies in the immune system that have specificity against blood group antigens.

Antigen

of the person may react with plasma or cells of another, especially during or after a blood transfusion. When incompatible blood is transfused, the antigen-antibody reactions within the recipient of transfusion cause systemic reactions.

types Febrile

Allergic

causes Recipient antibodies to donor leukocytes Bacterial contamination Recipient responds to

Rise in temperature within two hours after transfusion. chills Flushing, Hives, Itching,

donor proteins Severe immune response to a foreign substance

Dyspnea,Stridor,Hypotens ion

Acute hemolytic Administration of incompatible blood Preexisting antibodies against transfused RBCs Improper administration Delayed Extravascular hemolytic

symptoms

hemolysis of RBCs

Fever, chills, nausea, dyspnea, low back pain, hemoglobinurea, pain at transfusion site, tachychardia, hypotension Chills, pallor, fatigue, anemia, dyspnea, jaundice, unexpected drop of hemoglobin

An

autosomal recessive disease in which the normal amino acid, glutamic acid, is replaced by valine Stimulus for sickling: low oxygen tension • Sickle cell hemoglobin acquires a crystal-

like formation

Genetic defect Replacement of glutamic acid by valine Altered globin chain (HbS) Low oxgyen tension RBCs become sickled shape Blood vessel occlusion

•Microinfarction •Ischemic tissue pain •Ischemic organ malfunction •Autoinfarction of

Shortened red cell survival (hemolytic anemia) •Anemia •Jaundice •Gallstones

Disorders

that demonstrate large, immature, poorly functional erythrocytes. Causes: • Vitamin B12 deficiency (Pernicious

anemia) • Folate (Folic Acid) deficiency

Cause:

malabsorption of Vitamin B12 due to: • An autoimmune disease leading to

progressive loss of parietal cells in the stomach, causing failure of secretion of hydrochloric acid and intrinsic factor (Pernicious Anemia) Intrinsic factor: A glycoprotein essential to bind Vitamin B12 and protect it from degradation by intestinal enzymes.

• Increase in demand

Vitamin

B12:

• Normal functioning of the brain • Formation of blood

•Hereditary gastric mucosal atrophy •Autoimmune disorder •Gastric or small bowel surgery STOMACH Destruction/absence of parietal cells in the stomach Inability to form intrinsic factor

•Increased requirement – pregnancy •Intestinal parasites

Malabsorption of vitamin B12

Demand > supply

Faulty RBC production Anemia

NORMAL RBC

MEGALOBLASTIC ANEMIA

Inhibited

growth of all cells

• Anemia • Leukopenia • Thrombocytopenia

Demyelination

of Peripheral nerves to

spinal cord TRIAD SYMPTOMS:

• Weakness • Sore tongue • Paresthesia and other neurologic symptoms

 Folic

Acid

• Necessary for normal RBC production

 Causes:

• Poor dietary intake • Poor GI absorption • Folate antagonists (anticancer drugs and

anticonvulsants) • Inborn errors of metabolism • Increased requirement

 Effect:

impaired DNA synthesis and megaloblastic transformation of the RBCs

Characterized

by deficient hemoglobin synthesis caused by lack of iron. Cells become macrocytic and hypochromic because of low concentrations of hemoglobin. Most common type of anemia

Causes:

• Increase loss (hemorrhage and hookworm

infestations) • Decreased dietary intake Children Elderly Adolescents Indigents

• Pernicious anemia • Gastrectomy • Malabsorption syndromes

Clinical

manifestations

• Fatigue • Tachycardia • Irritability • Pallor • Sore tongue • Cheilosis • Koilonychia • Pica

Occurs

as a result of reduced bone marrow function Effect: Pancytopenia  drop in all levels of all blood elements. Causes: • genetic failure of bone marrow development • Injury to stem cells Viral infections Medications Toxins

Pathology:

• Marrow is hypocellular or is replaced with

fat