Classification of hemolytic anemias

Hereditary hemolytic anemias

Defects of the cell membrane:

- hereditary spherocytic anemia;

- hereditary elliptocytic anemia.

Defects of erythrocytic metabolism:

- glucose-6-phosphate dehydrogenase (G-6-PD) deficiency anemia.

Abnormal hemoglobins:

- sickle cell anemia;

- -thalassemia.

Acquired hemolytic anemia

Immunological destruction of red blood cells:

- transfusion with incompatible blood;

- hemolytic disease of the newborn;

- autoimmune hemolytic anemia (AIHA) (warm-active AIHA and cold-active AIHA).

Physical destruction of red blood cells:

-march hemoglobinuria;

- traumatic cardiac hemolytic anemia.

Hemolytic anemia induced by chemical agents.

Hemolytic anemia caused by microorganism:

- anemia of malaria;

- anemia of Clostridia.

Hemolytic anemia secondary to other disease.

Paroxysmal nocturnal hemoglobinuria.

Etiology

The causes of hemolytic anemias may be hereditary or acquired. The causes of hereditary hemolytic anemia are grouped into three categories: 1) defect of the cell membrane; 2) defects of erythrocyte metabolism; 3) abnormal hemoglobins.

Pathogenesis. Acquired hemolytic anemias have numerous causes hence corresponds with different pathogenesis. Destruction of red blood cells refers to inappropriate activation of the body's immune system and appearance either alloantibodies or autoantibodies. A number ingestion of drugs and chemicals may result to shortened life span of erythrocytes. Inflammation of blood vessels or presence of blood clots may interfere the structure and function of red blood cells and lead to early destruction. Such physical factors as vascular protheses, heart valves protheses cause accelerated hemolysis of red blood cells. Some infectious agents for example malaria parasite (Plasmodium falciparum, Clostridiax) use red blood cells for their propagation and this process destroy them. Hemolytic anemia could develop as a secondary effect of certain clinical condition such vitamin В₁₂ -deficiency anemia, splenomegalia, liver disease and renal failure.

Hemolysis may occur intravascularly or extravascularly. Hemoglobin liberated into the plasma is bound mainly by the alpha-2 globin, haptoglobin, to form a complex too large to be lost in the urine. It is taken up by the liver and degraded. Some hemoglobin is partially degraded and bound to albumin to form methemoglobin. If all the haptoglobin has been consumed, free hemoglobin may be lost in the urine. In small amounts this is reabsorbed by the renal tubules where the hemoglobin is degraded and the iron stored as hemosiderin. Sloughing of the renal tubular cells gives rise to hemosiderinuria which, if found, always indicates intravascular hemolysis. Hemoglobinuria occurs when greater amounts of hemoglobin are lost, giving the urine a black appearance (black water).

Extravascular hemolysis occurs in the phagocytic cells of the spleen, liver, bone marrow and other organs and there may be little or no depletion of haptoglobin.

Clinical features

Clinical features include three indications: anemia, jaundice and splenomegalia. The symptoms of anemia are common as most other one: weakness, fatigue, dyspnea, palpation, headache, dizziness, inability to concentrate. The most important sign of hemolytic anemia is jaundice, which differ from slightly yellow tint to intense lemon color of mucosa membrane, sclera and skin. Splenomegaly is specific sign, explained by hyperplasia of cells, which take part in phagocytosis. Commonly spleen is enlarged moderately.

Latent compensated hemolytic anemia explained by capacity of bone marrow to produce increased number of reticulocytes and in the peripheral circulation red blood cell counts may be fairly normal.

However the bone marrow will no longer be able to compensate and breakdown rate of erythrocytes becomes greater than the production rate of new erythrocytes. In acute cases is developed the hemolytic crisis with abrupt onset, high temperature, severe fatigue, nausea, vomiting pain in the abdomen, pronounced pallor with yellow color of mucosa and skin, hemorrhage lesions. Patient has grave condition, may be occur hemolytic coma. Tachycardia, systolic murmur, hypotension are observed. During palpation of abdomen the hepatosplenomegalia is detected.

Hemolysis may be acute, chronic, or episodic. Hemolytic crisis (acute, severe hemolysis) is uncommon; it may be accompanied by chills, fever, pain in the back and abdomen, prostration, and shock. In severe cases, hemolysis increases (jaundice, splenomegaly, and, in certain types of hemolysis, hemoglobinuria and hemosiderinuria), and erythropoiesis increases (reticulocytosis, hyperactive bone marrow). In chronic hemolysis, anemia may be exacerbated by aplastic crisis (temporary failure of erythropoiesis); this is usually related to an infection, often parvovirus.

Additional methods of examination

Clinical blood analysis:

- hemoglobin concentration decreased;

- red blood cells count decreased;

- reticulocytes increased;

- macrocytosis;

- polychromasia;

- polymorphonuclear.

Bone marrow:

- compensatory erythroid hyperplasia.

Biochemical blood analysis:

- increased plasma unconjugated bilirubin;

- increased urinary urobilinogen; increased faecal urobilinogen;

- increased plasma lactatdehydrogenasa.

Findings of intravascular hemolysis:

- reduced or absence of haptoglobin in the blood;

- presence of free hemoglobin in the blood;

- presence of free hemoglobin in the urine;

- presence of methemalbumemia.

Special test for determining RBC life span using the 51Cr.

 

Cause	Morphologic Changes	Special Features
Acute blood loss	Normochromic-normocytic, with polychromatophilia; hyperplastic marrow		If severe, possible nucleated RBCs and left shift of WBCs; leukocytosis and thrombocytosis
Chronic blood loss	Same as iron deficiency; severe hemorrhage has supervened	may show features of acute blood loss if recent
Iron deficiency	Microcytic, with anisocytosis and poikilocytosis; reticulocytopenia; hyperplastic marrow, with delayed hemoglobination		Possible achlorhydria, smooth tongue, and spoon nails; absent stainable marrow Fe; low serum Fe, increased total Fe-binding capacity; low serum ferritin; low RBC ferritin
Vitamin B12 deficiency	Oval macrocytes; anisocytosis; reticulocytopenia; hypersegmented WBCs; megaloblastic marrow	Serum Bl2 < 180 pg/mL (< 130 pmol/L); frequent GI and CNS involvement; positive Schilling test, elevated serum bilirubin; increased LDH, antibodies to intrinsic factor in serum (common), absent gastric intrinsic factor secretion
Folate deficiency	Same as vitamin B12 deficiency	Serum folate < 5 ng/mL (< 11nmol/L), RBC folate < 225 ng/mL RBCs (< 510 nmol/L); nutritional deficiency and malabsorption (sprue, pregnancy, infancy, alcoholism)
Acute hemolytic anemia	Normochromic-normocytic; reticulocytosis; marrow erythroid hyperplasia		Increased serum bilirubin and LDH; increased stool and urine urobilinogen; hemoglobinuria in fulminating cases, hemosiderinuria
Chronic hemolytic anemia	Normochromic-normocytic; reticulocytosis; marrow erythroid hyperplasia; basophilic stippling (especially in lead poisoning)		Increased serum bilirubin and LDH; shortened RBC life span; increased radio-Fe turnover; hemosiderinuria

Complete Blood Count (CBC)

In a complete blood count (CBC) a routine hematology screening includes the following determinations: white blood cell count (WBC), red blood cell count (RBC), hematocrit (Hct), hemoglobin (Hgb), and differential white cell count (Diff). The differential states the neutrophils, lymphocytes, monocytes, eosinophils, basophils, and any abnormal cells as a percent of the total WBC count.

A complete hematologic examination also includes the indices, which are mean cell volume (MCV), mean cell hemoglobin (MCH), and mean cell hemoglobin concentration (MCHC). In addition, a careful inspection of the peripheral blood smear is important, as is a sedimentation rate (Sed rate or ESR).

Clinical blood analysis

· RBC: Red Blood Cells 4.2- 5.9 million/mm3

· Hemoglobin (Hgb):

Males: 14- 18g/dL

Females: 12- 16g/dL

· Hematocrit (Hct)

Males 40 - 54%

Females: 37- 47%

· MCV: Mean Cell Volume: 86 - 98 fl

· MCH: Mean Cell Hemoglobin: 27 - 32 pg

· MCHC: Mean Cell Hemoglobin Concentration: 31 – 35g/dl

· Platelet Count: 150,000 - 400,000 / mm3

· WBC: White Blood Cells: 4,000-10,000/mm3

Differential:

Neutrophils	40-75%
Lymphocytes	15-45%
Monocytes	1-10%
Eosinophils	1-6%
Basophils	0-2%

 

· ESR

Red cell absolute values

These can be calculated from:

a) hematocrit;

b) hemoglobin estimation;

c) red cell count.

The International Committee for Standardization in Hematology has recommended that the following units be used (SI units): mean cell volume as "fl" (femtoliters), mean cell hemoglobin as "pg" (picograms) and mean cell hemoglobin concentration as "g/dl".

Red cell absolute values are analyzed using the formulas:

hematocrit (Hct) is the volume of packed red blood сells found in 100ml of blood. For example, a value of 46% implies that there are 46 ml of red blood cells in 100 ml of blood.

mean cell volume (MCV) describes the red cells in terms of individual cell size. It is given usually as a direct whiteout from the automated system. However, it can also be calculated by dividing the volume of packed cells (hematocrit) by the number of RBCs.

MCV = Hct* 1015 fl

Red cell count per litre

mean cell hemoglobin concentration (MCHC) measures the concentration of hemoglobin in grams per 100ml of RBCs.

MCHС = Hemoglobin in g% g m %

Hct

mean cell hemoglobin (MCH) is the hemoglobin content of each individual red blood cell and is calculated by dividing the hemoglobin by the red blood cell count.

MCH = Hemoglobin in gm% * 10 13 pg

Red cell count per litre

 

Colour index. Once the quantity of erythrocytes and hemoglobin in a given blood specimen is known, it is possible to calculate the hemoglobin content of each erythrocyte. There are many methods by which hemoglobin saturation can be determined. One of them is the calculation of the colour index. This is a conventional value derived from the ratio of hemoglobin to the number of erythrocytes. This value is found by dividing a triplet quantity of hemoglobin in grams by the first three figures expressing the quantity of erythrocytes. Normally this value approaches 0,85-1.1. If it is less than 0,8, the erythrocyte saturation of hemoglobin is insufficient; it the value exceeds 1,1 the volume of erythrocytes is higher than normal.

Red blood cell morphology can be determined from a thin blood film stained with Romanowsky dyes. The three basic features of a red blood cell are its size, its shape and its inclusions.

Size of erythrocytes. Normal erythrocyte is nearly uniform in size with diameter of 7,2 to 7,9 nm. An increasing and decreasing in the size of a red blood cell is known as anisocytosis.

Shape of normal erythrocytes is a biconcave disc, which is thickest at its edges. The presence of many abnormal shapes on a blood smear is known as poikilocytosis.

Inclusions in erythrocytes. The normal red blood cell filled mainly with hemoglobin. In pathological states blood films will show red blood cells with colored spots or rings inside their cytoplasm.

Howell-Jolly bodies. These are small, well-defined, round, densely staining basophilic inclusion bodies about 1 urn in diameter, which usually occur singly but sometimes in multiples. They appear after splenectomy and are also seen in cases of severe anemia from a variety of causes. They contain DNA and may be chromosomal remnants or nuclear fragments.

Cabot rings. These are blue-staining, threadlike inclusions in the red cells in severe anemia. They may appear as rings, or twisted and convoluted in a variety of shapes. They may occupy the entire periphery of the cell but frequently are much smaller. They are not often seen. It has been postulated that they are remnants of the mitotic spindle, but others have found that they contain histone and iron.

Heinz bodies can be seen with special supravital stains such as methylviolet Heinz bodies are granules of precipitated hemoglobin.

Normal WBC count

The normal WBC count is usually between 4500 and 11,000/mm3 and may vary in a particular individual at different times of the day. A minor variation outside the normal range is not significant as long as the differential count and the peripheral blood smear are both normal. However, some early disorder, whether infectious or myeloproliferative, is not necessarily ruled out.

Mild to moderate leukocytosis (11,000-17,000/mm3): mild to moderate elevation of the WBC count usually indicates infectious disease, mainly of bacterial etiology. Usually, the leukocytosis increases with the severity of the infection. However, there are exceptions to this rule, particularly in elderly patients in whom severe sepsis can coexist with only a modest leukocytosis. As mentioned previously, the differential WBC count is of additional help.

Leukemoid reaction: occasionally such massive leukocytosis accompanies a systemic disease that the blood picture of leukemia is simulated. When a blood picture looks like leukemia but is not, the term "leukemoid reaction" is used. Severe sepsis, miliary tuberculosis, and other nonmalignant infectious conditions are among the more common causes.

In the differentiation of myelogenous leukemia versus leukemoid reaction determination of the leukocyte alkaline phosphatase is helpful. This enzyme is high in leukemoid reaction and is decreased in myelogenous leukemia. Also, the presence of Philadelphia antigen is specific for the majority of cases of chronic myeloid leukemia.

Leukopenia: a decreased absolute WBC count (leukopenia) can be mild (3000-5000/mm3), moderate (1500-3000/mm3), or extremely severe (<1500/mm3), and may be associated with diminution of the WBC count as a whole, decreases in neutrophils, or diminution of all the blood particles (pancytopenia).

Complete Blood Count (CBC)

Test	Name	Increased/Decreased
WBC	White Blood Cell	May be increased with infections, inflammation, cancer, leukemia; decreased with some medications (such as methotrexate), some autoimmune conditions, some severe infections, bone marrow failure, and congenital marrow aplasia (marrow doesn't develop normally)
% Neutrophil	Neutrophil/Band/Seg/Gran	This is a dynamic population that varies somewhat from day to day depending on what is going on in the body. Significant increases in particular types are associated with different temporary/acute and/or chronic conditions. An example of this is the increased number of lymphocytes seen with lymphocytic leukemia
% Lymphs	Lymphocyte
% Mono	Monocyte
% Eos	Eosinophil
% Baso	Basophil
RBC	Red Blood Cell	Decreased with anemia; increased when too many made and with fluid loss due to diarrhea, dehydration, burns
Hgb	Hemoglobin	Mirrors RBC results
Hct	Hematocrit	Mirrors RBC results
MCV	Mean Cell Volume	Increased with B12 and Folate deficiency; decreased with iron deficiency and thalassemia
MCH	Mean Cell Hemoglobin	Mirrors MCV results
MCHC	Mean Cell Hemoglobin Concentration	May be decreased when MCV is decreased; increases limited to amount of Hgb that will fit inside a RBC
Platelet	Platelet	Decreased or increased with conditions that affect platelet production; decreased when greater numbers used, as with bleeding; decreased with some inherited disorders (such as Wiskott-Aldrich, Bernard-Soulier), with Systemic lupus erythematosus, pernicious anemia, hypersplenism (spleen takes too many out of circulation), leukemia, and chemotherapy
MPV	Mean Platelet Volume	Vary with platelet production; younger platelets are larger than older ones

 

.

Literature

1. Internal diseases an introductory course. - Vasilenko V., Grebenev A. - M.: Mir. Publishers, 1990. - 647 p

2. Propedeutics to internal medicine. Part 1.-Vinnytsya: NOVA KNYHA, 2006.- 424 p.

3. Propedeutics to internal medicine. Part 2.-Vinnytsya: NOVA KNYHA, 2007.- 264 p.

4. Introduction to the course of internal diseases. Book 1. Diagnosis: [Textbook/Zh.D. Semidotskaya, O.S. Bilchenko, et al.].-Kharkiv: KSMU, 2005. -312p.

5. Michael Swash Hutchison’s clinical methods / XIX edition. ELBS, 1989. -618p.

6. Mark H., Beers M.D., Robert Berkow The Merck Manual of diagnosis and therapy / XVII edition.- Published by Merk research laboratories, 1999.- 2833 p.

7. Harrison΄s principles off internal medicine / Fauci, Braunwald, Isselbacher and al.-XIV edition. - Vol. 1 and 2. - International edition, 1998.

 

 

Topic 15. Hemorrhagic syndromes and the pathology of blood coagulation system. The syndrome of disseminated intravascular blood micro coagulation

Class lasts: 3 hours

Chronological class structure:

Control of initial standard of knowledges- 20 min.

Teacher′s demonstration of practical skills - 60 min.

Sudents′ independent work: - 30 min.

Control of ultimate standard of knowledges- 15 min.

Sum up of the class, homework- 10 min.

Questions for theoretical preparation: The main components of blood coagulation system. The factors of bleeding development and the reasons of hemorrhagic syndromes thrombocytopenia, coagulopathy and hemorrhagic vasculitis. The characteristics of hemorrhagic syndrome in hemophilia, thrombocytopenia purple and Shenljan-Jenoh disease. The manifestations of articulate, abdominal, renal and anemia syndromes in all these diseases. The main methods of laboratory diagnostics of hemorrhagic syndromes. The reasons of development and the pathogenesis of disseminated intravascular coagulation syndrome. The stages and clinical manifestation of DIC-syndrome, its main laboratory criteria.

 

The three major components of the hemostatic mechanism are: the platelets, blood vessels, and the plasma protein factors involved in coagulation and fibrinolysis.

The function of platelets in hemostatic process:

- platelet are the instrumental in maintaining the integrity of the endothelial lining of the blood vessels;

- platelet play a major role in repairing any injury in the vascular system, especially at the microcirculatory level;

- platelets take part in regulation of local inflammatory reaction and immune damage initiation;

- platelets are responsible for the specific reaction related to the formation of hemostatic plug.

There are three stages of platelets activation:

- signal transduction from platelet membrane lo the structure responsible for the specific reaction;

- platelet adhesion, release of chemical substances of platelet, aggregation and finally formation a plug or clot in vessel damage.

 

The chemical substances of platelet include a number of enzyme, epinephrine, norepinephrine, ATP and ATP-ase. Many specific compounds participating in clotting of the blood have been revealed in platelets. There are called thrombocytic or platelet factors and are designated by Arabic numerals.

The liquid state of the blood and the closed uninterrupted system of blood vessels in which blood circulates are the principal conditions for body functioning. They are provided by the system of blood coagulation (hemocoagulation system). It keeps blood in a liquid state and restores the wholeness of the pathways of its circulation by formation of blood thrombi (plugs, clots) in the damaged vessels.

The coagulation blood system comprises blood and tissues which produce, utilize and secrete substances from the body that are indispensable for the process of coagulation. The neurohumoral apparatus also belongs to this system.

The coagulation of blood is the process of clotting of whole blood, which results in the formation of a fibrin clot. Three processes are involved in blood clotting such as formation of prothrombinase, thrombin and fibrin. In addition, the phase preceding and the phase following blood coagulation are distinguished. The primary phase is accompanied by vascular thrombocytic hemostasis (i.e. processes involved in stoppage of bleeding) in which bleeding from the microcirculatory vessels with low blood pressure is arrested. This process is also known as microcirculatory hemostasis. In the second phase two processes simultaneously occur, i.e. retraction and fibrinolysis of the blood clot. Thus, the process of hemostasis involves three components: vessel walls, formed blood elements, and enzymatic plasma system of blood clotting.