NotesAnemia definition and classification

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Anemia definition and classification

Unread post by wadbadi73 » 06 May 2015, 20:02

Definition and classification of anemia
In its broadest sense, anemia is a functional inability of the blood to supply the tissue with adequate O2 for proper metabolic function. Anemia is not a disease, but rather the expression of an underlying disorder or disease. Anemia is usually associated with decreased levels of hemoglobin and/or a decreased packed cell volume (hematocrit), and/or a decreased RBC count.
Classification: There are two main ways to classify the anemias:

A. Morphological (based on red cell size and hemoglobin content)

(1) Microcytic hypochromic anemia
(MCV < 80 mcm 3, diameter of erythrocyte < 6,5 mcm)
(2) Macrocytic hyperchromic
(MCV - mean corpuscular volume >100 mcm3, diameter of erythrocyte > 8 mcm)
(3) Normocytic normochromic
(MCV = 81-99 mcm 3, diameter of erythrocyte = 7,2-7,5 mcm)
B. Pathophysiological (based on causative factors)
(1) Blood Loss
(2) Impaired RBC production
(3) Increased RBC destruction

Pathophysiological Classification of Anemias
I. Blood Loss Anemia
A. Acute post hemorrhagic anemia
B. Chronic post hemorrhagic anemia
II. Impaired RBC Production
A. Disturbance of the proliferation and differentiation of stem cells
1. Multipotential stem cells
a. Aplastic anemia
2. Unipotential stem cells
a. Pure red cell aplasia
b. Anemia of renal failure
c. Anemia of endocrine disease
B. Disturbance of the proliferation and maturation of differentiated stem cells
1. Defective DNA synthesis (megaloblastic anemia):
a. Vitamin B12 deficiency
b. Folic acid deficiency
2. Defective hemoglobin synthesis (hypochromic anemias):
a. Iron deficiency anemia (defective heme synthesis)
b. Thalassemia (defective globin synthesis)
3. Unknown or multiple mechanisms
a. Anemia associated with bone marrow infiltration
b. Anemia of chronic disease
c. Lead poisoning
d. Sideroblastic anemia
III. Increased RBC Destruction (Hemolytic Anemias)
A. Intrinsic Disorders
1. Membrane Defects
a. Hereditary spherocytosis
b. Hereditary ovalocytosis
c. Hereditary acanthocytosis (rare)
d. Hereditary stomatocytosis (rare)
e. Paroxysmal nocturnal hemoglobinuria (PNH)
2. Metabolic Defects
a. Glucose-6-phosphate dehydrogenase deficiency
b. Pyruvate kinase deficiency
3. Hemoglobin Defects
a. Hemoglobinopathies
b. Thalassemia
B. Extrinsic Disorders
1. Chemical Agents
2. Vegetable and Animal Poisons
3. Infectious Agents
4. Physical Agents
a. Heat
b. Traumatic hemolysis (Red Cell Fragmentation Syndrome)
5. Immunologically Caused Hemolytic Anemias
:D Wadbadi :D

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