Anemia, Iron Deficiency

KEY FEATURES

Essentials of Diagnosis

• Iron deficiency is present if

  • Serum ferritin is < 12 ng/mL or

  • < 30 ng/mL if also anemic

• Caused by bleeding unless proved otherwise

• Responds to iron therapy

General Considerations

• Most common cause of anemia worldwide

• Causes (see Table 15–3)

• Most important cause in adults is chronic blood loss, especially menstrual and gastrointestinal (GI) blood loss

• Women with heavy menstrual losses

  • May require more iron than can reasonably be absorbed

  • Will almost always become iron deficient without iron supplementation

• Pregnancy and lactation

  • Increase requirement for iron

  • Medicinal iron is needed during pregnancy and lactation

• Search for a source of GI bleeding if other sites of blood loss (menorrhagia, other uterine bleeding, and repeated blood donations) are excluded

• Long-term aspirin use and nonsteroidal anti-inflammatory drugs

  • May cause blood loss

  • Even without documented structural lesion

Celiac disease (even asymptomatic) can cause iron deficiency through poor absorption in the GI tract

• Intravascular hemolysis

  • Traumatic hemolysis due to a prosthetic cardiac valve

  • Paroxysmal nocturnal hemoglobinuria)

• The cause of iron deficiency is not found in up to 5% of cases

• Iron deficiency refractory to oral iron replacement

  • Refractoriness is a hemoglobin increment < 1 g/dL (10 g/L) after 4–6 weeks of 100 mg/day of elemental oral iron

  • Causes include

    • Malabsorption from autoimmune gastritis

    • Helicobacter pylori gastric infection

    • Celiac disease

    • Hereditary iron-refractory iron deficiency anemia (rare autosomal recessive disorder due to mutations in the transmembrane serine protease 6 gene which normally downregulates hepcidin)

CLINICAL FINDINGS

Symptoms and Signs

• Easy fatigability

• Tachycardia

• Palpitations

• Dyspnea on exertion

• Skin and mucosal changes in severe deficiency

  • Smooth tongue

  • Brittle nails

  • Spooning of nails (koilonychia)

  • Cheilosis

• Dysphagia

  • From esophageal webs (Plummer-Vinson syndrome)

  • May occur in severe iron deficiency

• Pica develops in many iron-deficient patients

  • Craving for specific foods (eg, ice chips, lettuce) not rich in iron

Differential Diagnosis

• Microcytic anemia resulting from other causes

  • Anemia of chronic disease

  • Thalassemia

  • Lead poisoning

  • Zinc deficiency

DIAGNOSIS

Laboratory Tests

• Stages of iron deficiency

  • Depletion of iron stores without anemia occurs first

  • Then anemia with a normal red blood cell (RBC) size (normal MCV)

  • Followed by anemia with reduced RBC size (low MCV)

• Diagnosis can ...