Morfopatologie.usmf.md



Red and white blood cells disorders

Introduction

Anemia, Signs and Symptoms, Basic Mechanisms, Red Cell Loss.

Leukemias, Myeloid, Lymphocytic,

Plasma cell discrasias, plasma cell myeloma,

Introduction

The organs and tissues involved in hematopoiesis have been traditionally divided into myeloid tissue, which includes the bone marrow and the cells derived from it (e.g., erythrocytes, platelets, granulocytes, and monocytes), and lymphoid tissue, consisting of thymus, lymph nodes, and spleen. This subdivision is artificial with respect to both the normal physiology of hematopoietic cells and the diseases affecting them. For example, although bone marrow is not where most mature lymphoid cells are found, it is the source of lymphoid stem cells. Similarly, myeloid leukemias, neoplastic disorders of myeloid stem cells, originate in the bone marrow but secondarily involve the spleen and (to a lesser degree) lymph nodes. Some red cell disorders (hemolytic anemias) result from the formation of autoantibodies, signifying a primary disorder of lymphocytes. Thus, it is not possible to draw neat lines between diseases involving the myeloid and lymphoid tissues. Recognizing this difficulty, we somewhat arbitrarily divide diseases of the hematopoietic tissues into two chapters. In the first, we consider diseases of red cells and those affecting hemostasis. In the second, we discuss white cell diseases and disorders affecting primarily the spleen and thymus.

Lymphocytes and monocytes not only circulate in the blood and lymph but also accumulate in discrete, organized masses within lymph nodes, thymus, spleen, tonsils, adenoids, and Peyer patches. Less discrete collections of lymphoid cells occur in the bone marrow, lungs, gastrointestinal tract, and other tissues. Lymph nodes are the most widely distributed and easily accessible component of the lymphoid tissue and hence are frequently examined for diagnosis of lymphoreticular disorders. Before discussing these pathologic states, we will briefly review the normal morphology of lymph nodes

OBJECTIVES:

• Understand the origin and development of blood cells.

• Understand the clinical significance of decreased numbers of circulating blood cells (cytopenias) and increased numbers of circulating blood cells (cytosis or cytophilia).

• Know the methods of classifying anemias.

• Know some of the more common anemia types.

• Understand leukemias as systemically distributed neoplasms of white cells generally arising from the bone marrow and know the differences between acute and chronic leukemias and myelogenous and lymphocytic leukemias.

• Understand malignant non-Hodgkin's lymphoma and Hodgkin's disease as solid tumors of the hematopoietic system, their cells of origin, their variable morphologic presentation, how they are classified, and some of the special techniques used to study them.

• Understand that the plasma cell is an end stage functional B lymphocyte and appreciate a spectrum of disorders of plasma cells, including multiple myeloma.

• Develop an understanding of the approach to patients who present with 1) peripheral blood cytopenias and 2) lymphadenopathy.

Key words: blast; acute myelogenous leukemia; acute lymphocyte leukemia; chronic myelogenous leukemia; chronic lymphocyte leukemia; Auer rod; cytogenetics; immunophenotype, gammopathy; myeloma cells; Bence Jones protein.

Clinical OBJECTIVES:

1. Describe the bone marrow cellularity and peripheral blood counts in aplastic anemia.

2. Describe the morphologic changes in the blood and bone marrow in anemia associated with vitamin B12 and folate deficiency. Define ineffective hematopoiesis and nuclear maturation defects.

3.

DISEASES OF ERYTHROCYTES:

ANEMIA

Anemia is a reduction below normal limits of the total circulating red cell mass resulting in diminished oxygen transport capacity of the blood.

Signs and Symptoms of Anemia

1. pallor of skin and mucous membranes

2. tachycardia, possibly with heart murmur

3. tachypnea

4. dyspnea on exertion

5. headache

6. fever

7. koilonychia, cheiliosis--iron deficiency

8. jaundice--intravascular hemolysis

Physiologic Adjustments to Anemia

The degree of symptomatology will depend on 1) the severity of anemia and 2) the acuity with which the anemia develops.

Many physiologic adjustments may occur to compensate for the affects of anemia:

1. shift to the right of the oxygen dissociation curve. This occurs due to an increase in 2,3 DPG and leads to an increase in p50, the partial pressure of oxygen at which hemoglobin is 50% saturated. The effect is to cause more oxygen unloading in the tissues.

2. shunting of blood away from skin, mesenteric bed, and kidneys

3. increased cardiac output

4. erythroid hyperplasia of the bone marrow stimulated by elevated erythropoietin

Basic Mechanisms of Anemia

Normally, in every individual there is a carefully maintained balance between red cell senescence and the generation of new red cells by the marrow to replace them. In spite of this, anemias not only occur but are one of the most commonly encountered clinical problems.

Despite the myriad number of specific anemia syndromes, it is useful to remember that all mechanisms of anemia can be reduced to one of three types:

1. excess red cell loss

2. shortened red cell survival

3. decreased red cell production

Decreased Red Cell Survival

Decreased red cell survival in the circulation generally is synonymous with hemolysis. The factors causing hemolysis may either be intrinsic to the red cell itself--a defect in the cell structure or content--or extrinsic to the red cell and independent of it.

• intrinsic defects

o RBC membrane abnormalities

o RBC enzymopathies

o hemoglobin disorders

• extrinsic defects

o immune mediated hemolysis

o physical mediators of hemolysis

 Decreased Red Cell Production

In these anemias, the bone marrow is unable to produce sufficient red cells to maintain the patient's hematocrit in the normal range. Typically, the reticulocyte count is low. The bone marrow may be hypocellular, normocellular, or hypercellular.

Bone marrow, normal and aplastic anemia

A hypo- or normocellular marrow is abnormal, as a compensatory erythroid hyperplasia would usually be expected. Conversely, a hypercellular marrow with a low reticulocyte count indicates ineffective erythropoiesis.

1. Iron deficiency

Iron is an essential element widely distributed in the body, although most its found in the erythron.

| Distribution of Body Iron |

| Hemoglobin | 2.5 gm | (63 %) |

| Ferritin | 1.4 gm | (33 %) |

| Myoglobin | 0.16 gm | ( 4 %) |

| Plasma | 0.003 gm | ( ................
................

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