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نشر في 02-23-2022 11:59 PM
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Anemia, General Principles
• Definition → Hb < 13.5 g/dL (Hct < 40) in men or Hb < 12 g/dL (Hct < 37) in women
• Most useful classification of anemia (based on MCV or mean corpuscular volume):
1. Microcytic (MCV < 80) → Iron-deficiency anemia, sideroblastic anemia, anemia of chronic disease, lead poisoning, thalassemia
2. Normocytic (MCV 80-100) → aplastic anemia, anemia of chronic disease, myelofibrosis/bone marrow infiltration, chronic renal failure, hemolytic anemia,
early stages of iron-deficiency anemia, hemorrhage
3. Macrocytic (MCV > 100) → megaloblastic anemia (vitamin B12 and/or folate deficiency; drug-induced), liver disease, myelodysplasia, reticulocytosis
• Best initial diagnostic tests : CBC with RBC indices (e.g. MCV), reticulocyte count, blood smear
1-Microcytic Anemia
Iron-deficiency Anemia
• Most common cause of anemia
• Females > Males
• Etiology:
1. Chronic blood loss à most common cause; e.g. GI cancer, menorrhagia
2. ↓ dietary intake/malabsorption e.g. celiac disease, post-gastrectomy, cow’s milk diet in infants.
3. ↑ requirements → e.g. pregnancy, growth spurt
4. Chronic intravascular hemolysis → hemoglobinuria, hemosiderinuria
• Clinical features specific for iron-deficiency anemia
1. brittle nails/koilonychia (spoon-shaped nails)
2. glossitis/angular cheilitis
3. pica (craving for non-nutritive substances)
4. dysphagia (Plummer-Vinson syndrome)
• Initial lab results (CBC, reticulocyte count, etc.) → low Hb and/or Hct, low MCV, ↑ RDW (red blood cell distribution width), ↓ reticulocyte count, possible thrombocytosis
• Blood smear → hypochromic, microcytic RBCs poikilocytosis (abnormal shapes)
• Best next step → perform iron studies:
1. ↓ serum ferritin → most specific laboratory test; lacks sensitivity (falsely elevated in inflammatory conditions, liver disease and/or malignancies)
2. ↓ serum iron
3. ↑ TIBC (total iron binding capacity)
4. ↓ transferrin saturation (serum iron/TIBC ratio, expressed as %)
• Most accurate diagnostic test à bone marrow biopsy + Prussian blue stain
Anemia of Chronic Disease
• Anemia that accompanies any chronic inflammatory
and/or malignant condition
• Pathophysiology →
1. ↓ sensitivity to erythropoietin
2. Impaired utilization of stored iron due to ↑ levels of TNF-α and IL-6
• Clinical features : symptoms/signs of anemia + that of the underlying disease
• Initial lab results : low Hb and/or Hct, low or normal MCV, ↓ reticulocyte count, normal RDW
• Blood smear → hypochromic, microcytic or normochromic, normocytic RBCs
• Best next step → perform iron studies:
1. ↓ serum iron
2. ↓ TIBC
3. Normal transferring saturation
4. Normal or ↑ serum ferritin
• Bone marrow biopsy + Prussian blue stain → ↑stainable iron
Thalassemia
• A group of hereditary (autosomal recessive) disorders characterized by decreased to absent globin chain (α and/or β) synthesis → hypochromic, microcytic anemia
• α-thalassemia (common in Asians and African-Americans)
• β-thalassemia (common in people of Mediterranean origin; also seen in Asians and/or African-Americans) unbalanced production of α-chains leads to ineffective
erythropoiesis, chronic hemolysis and extramedullary hematopoiesis
• Best initial step → perform iron studies to rule out iron-deficiency (should be normal in both forms of thalassemia)
• Best next and the most sensitive test is hemoglobin electrophoresis:
1. α-thalassemia : normal levels of HbA2 and HbF
2. β-thalassemia
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