Anemia: Causes, Classification, and Symptoms PDF

Anemia An abnormal decrease in red blood cells and/or hemoglobin concentration reducing the ability of blood to carry adequate amounts of oxygen to tissues. Clinically, anemia is usually defined by a hemoglobin less than 14 g/dl in males, and less than 12 g/dl in females. Anemia is not a final di...

Anemia An abnormal decrease in red blood cells and/or hemoglobin concentration reducing the ability of blood to carry adequate amounts of oxygen to tissues. Clinically, anemia is usually defined by a hemoglobin less than 14 g/dl in males, and less than 12 g/dl in females. Anemia is not a final diagnosis in itself; rather, it is an objective sign of disease. When an anemia is identified, it must be investigated further to determine its underlying cause. [Classification of Anemia by Etiology ] **Inadequate erythropoiesis** *These anemias are characterized by a low reticulocyte count.* Common causes include: - Lack of some nutrient essential for RBC production or hemoglobin synthesis (iron, B12, folate, B6, protein). - Injury to bone marrow stem cells (e.g., immunologic, toxic, radiation). - Replacement of bone marrow stem cells by a neoplasm (metastatic cancer, leukemia, lymphoma). - Injury to bone marrow stem cells (i.e., aplastic anemia). - Chronic disease that interferes with normal protein metabolism, erythropoietin synthesis, or iron metabolism/utilization (Examples include inflammatory diseases such as systemic lupus erythematosus or rheumatoid arthritis, cancer, endocrine deficiencies such as hypothyroidism, chronic renal failure, etc.) **Loss of RBC's from the circulation (i.e., Hemorrhage)** The most frequent sites of chronic bleeding are the gastrointestinal and genitourinary tracts. With adequate bone marrow function, a hemorrhagic anemia will manifest with an increased reticulocyte count. Loss of RBC from circulation can eventually lead to an iron deficiency anemia because of the loss of iron in the hemoglobin. **Shortened RBC life span within the circulation (i.e., Hemolysis)** Anemia results from accelerated rates of RBC destruction that is greater than the bone marrow's ability to replace the lost RBC's. Key clinical feature of hemolysis is an increased reticulocyte count and laboratory indicators of hemolysis (elevated unconjugated bilirubin, LDH). **Dilutional (spurious) anemia** A low hematocrit caused by increased plasma volume. The total number of RBC's is normal, but they are "diluted" by expanded plasma volume. Commonly associated with third trimester of pregnancy, congestive heart failure, some forms of renal failure and administration of intravenous fluids. Not a true anemia and is corrected by correcting fluid balance. [Classification of Anemia by Cell Morphology] **Cell size** Macrocytic Normocytic Microcytic **Laboratory Evaluation of RBC size** Mean cell volume (MCV) *Average volume of the RBCs* Red blood cell distribution width (RDW) *Amount of variability in the RBC diameter* **Hemoglobin Content** Hyperchromic Normochromic Hypochromic **Laboratory Evaluations of Hemoglobin Content** Mean cell hemoglobin (MCH) or mean cell hemoglobin concentration (MCHC) **Changes in shape seen on peripheral blood film (smear)** Poilkilocytes *Seen with artificial heart valves, hemolytic anemia, iron deficiency, thallassemia, megaloblasic anemia, myelodysplasia\...* Anisocytosis *Presence of RBCs of varying sizes* Abnormal morphologies *Sickle cells, spherocytes, target cells, elliptocytes\....* *Microcytic-Hypochromic Anemia* **General Pathophysiology** Erythrocytes are usually abnormally small and contain reduced amounts of hemoglobin. Iron Deficiency Anemia [Epidemiology] Most frequently diagnosed anemia in U. S./worldwide Incidence higher in females (4-6%) than males (4%) [Etiologies] **Chronic bleeding** (\* = most common causes) Bleeding from the gastrointestinal tract Bleeding from the urinary tract (hematuria) \*Menstruation in females (blood loss 10-250 ml/month) Less common causes of blood loss and iron deficiency include benign and malignant uterine tumors, frequent blood donations, pulmonary hemosiderosis (hemoptysis and pulmonary fibrosis), and hook worm infection. **Inadequate dietary iron** - Populations at risk! Strict vegetarians: unless their diet includes iron rich foods or is supplemented with iron Pregnancy: increased demands on maternal iron stores Infants fed cow\'s milk: Fe is in breast milk and infant formula Young children: increased nutrient demand with growth, limited diet Adolescents: Growth spurts, poor diet, beginning of female menstruation Elderly: decreased meat intake, decreased Fe absorption **Malabsorption** Inflammatory bowel disease, celiac disease H. Pylori infection leading to duodenal ulcers [Pathophysiology] *Slow onset* Stage I: depletion of iron stores, increase in apotransferrin production Stage II: iron-deficient erythropoiesis begins Stage III: small, Hb-deficient RBCs enter circulation, replacing normal erythrocytes; negative feedback to bone marrow results in decreased erythropoiesis [\ ] [Laboratory Evaluation ] **Evaluation of iron stores** Low plasma ferritin (\< 12-15 µg/dl) *Iron studies (generally not necessary)* Decreased plasma (serum) iron (usually \< 40-60 µg/dl) Increased total iron binding capacity (TIBC) (usually \> 410 µg/dl) Increased transferrin (really a measure of apotransferrin) Decreased transferrin saturation (really a measure of apotransferrin saturation) **\ ** **Evaluation of the anemia** Low MCV (\< 80) (and small RBC's on stained blood smear) Low MCH (\