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Definition: Low oxygen-carrying capacity of blood, shown by low level of hemoglobin (Hb) or low number of circulating RBCs in blood.
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Depends on acuity, severity, and patient age:
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Acute anemia: Symptoms of hypovolemia—tachycardia (first sign), postural hypotension (second sign), and shock.
Chronic anemia: Often asymptomatic if mild and chronic; fatigue, dyspnea on exertion, postural lightheadedness, pallor, headache, systolic ejection murmur if moderate to severe.
Elderly patients may exhibit worsening angina, claudication, and possibly HF.
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Workup: Begin by categorizing the possible causes by MCV. Next, look at reticulocyte count (hyper- or hypoproliferative). The etiology is often multifactorial, but the basic algorithm and possible causes are shown in Figure 7.1.
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KEY FACT
Assume GI bleed for men and postmenopausal women until proven otherwise!
Menstrual blood loss is the most common cause in premenopausal women.
Iron deficiency due to nutritional deficiency is most common in children (especially with excessive cow's milk intake).
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Iron Deficiency Anemia (IDA)
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Etiologies generally include blood loss (eg, GI losses, surgical blood loss, menstrual blood loss, GI parasites), malabsorption (eg, gastrectomy, gastritis and Heliobacter pylori, bariatric surgery, celiac disease), ↑ demand for iron (hemodialysis, pregnancy, rapid growth coupled with inadequate diet).
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The following symptoms are not sensitive or specific; lab studies should be done to diagnose IDA.
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Mostly asymptomatic if mild.
If severe: Fatigue, pallor, ↓ exercise capacity.
If severe and prolonged:
Angular cheilosis: Fissures at the corners of the mouth.
Atrophic glossitis.
Pica: Craving for nonnutritive substances.
Koilonychia: Spooning of the fingernails and brittle nails.
Plummer-Vinson syndrome: Esophageal webs and atrophic glossitis, leading to dysphagia.
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MNEMONIC
Causes of microcytic anemia:
TICS
Thalassemia
Iron deficiency
Chronic disease
Sideroblastic anemia
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CBC with smear: ↓/normal MCV, ↑ RDW, microcytic, hypochromic RBCs, and variation in RBC size (anisocytosis) or shape (poikilocytosis). No target cells!
Iron studies: ↓ serum iron, ↑ transferrin iron-binding capacity (TIBC), ↓ transferrin saturation, and ↓ serum ferritin.
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KEY FACT
Always order a smear for the diagnosis of microcytic anemia.
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Differential Diagnosis
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KEY FACT
↑ HbA2 on electrophoresis is diagnostic of α-thalassemia.
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