Anemia Introduction

Anemia Introduction

• Anemia is a group of diseases characterized by a decrease in hemoglobin (Hb) or red blood cells (RBCs), resulting in decreased oxygen-carrying capacity of blood.
• The World Health Organization defines anemia as Hb less than 13 g/dL in men or less than 12 g/dL in women.

Pathophysiology

• Functional classification of anemias is based on cell size.
• Morphologic classifications are based on cell size, including:
  • Macrocytic cells, larger than normal, associated with deficiencies of vitamin B12 or folic acid.
  • Microcytic cells, smaller than normal, associated with iron deficiency.
  • Normocytic anemia, associated with recent blood loss or chronic disease.

Iron-Deficiency Anemia (IDA)

• Characterized by decreased levels of ferritin (most sensitive marker) and serum iron, and decreased transferrin saturation.
• Caused by inadequate dietary intake, inadequate gastrointestinal absorption, increased iron demand, blood loss, and chronic diseases.

Vitamin B12-Deficiency Anemia

• Characterized by macrocytic anemia, caused by inadequate dietary intake, malabsorption syndromes, and inadequate utilization.
• Deficiency of intrinsic factor causes decreased absorption of vitamin B12 (pernicious anemia).

Folic Acid-Deficiency Anemia

• Caused by inadequate dietary intake, hyperutilization due to pregnancy, hemolytic anemia, malignancy, chronic inflammatory disorders, long-term dialysis, or growth spurt.
• Deficiency can be caused by drugs reducing absorption of folate or through folate antagonism.

Anemia of Inflammation (AI)

• Characterized by decreased serum iron, but normal or increased serum ferritin concentration.
• Associated with malignant, infectious, or inflammatory processes, tissue injury, and conditions associated with release of proinflammatory cytokines.

Clinical Presentation

• Acute-onset anemia: characterized by cardiorespiratory symptoms.
• Chronic anemia: characterized by weakness, fatigue, headache, orthopnea, dyspnea on exertion, vertigo, faintness, cold sensitivity, pallor, and loss of skin tone.
• Iron deficiency anemia: glossal pain, smooth tongue, reduced salivary flow, pica, and pagophagia.
• Vitamin B12 deficiency: neurologic effects (numbness, paraesthesis), psychiatric findings (irritability, depression, memory impairment).

Diagnosis

• Rapid diagnosis is essential because anemia is often a sign of underlying pathology.
• Initial evaluation involves complete blood cell count (CBC), reticulocyte index, and examination of stool for occult blood.
• Decreased serum ferritin is the earliest and most sensitive laboratory change for IDA.
• Mean corpuscular volume is usually elevated in macrocytic anemias.

Treatment

Iron-Deficiency Anemia

• Oral iron therapy with soluble ferrous iron salts at a daily dosage of 150-200 mg elemental iron in two or three divided doses.
• Parenteral iron preparations are available for patients with iron malabsorption, intolerance of oral iron therapy, or nonadherence.

Vitamin B12-Deficiency Anemia

• Oral vitamin B12 supplementation is as effective as parenteral, even in patients with pernicious anemia.
• Parenteral therapy acts more rapidly than oral therapy and is recommended if neurologic symptoms are present.

Folate-Deficiency Anemia

• Oral folic acid supplementation of 1 mg daily for 4 months is usually sufficient for treatment.

Anemia of Inflammation

• Treatment focuses on correcting reversible causes, reserving iron therapy for established IDA.
• RBC transfusions are effective but should be limited to Hb of 7-8 g/dL.
• Erythropoiesis-stimulating agents (ESAs) can be considered, but response can be impaired in patients with AI.

Pediatric Populations

• Infants aged 9-12 months: Administer ferrous sulfate 3-6 mg/kg/day (elemental iron) divided once or twice daily between meals for 4 weeks.
• Vitamin B12 and folic acid dosages should be titrated according to clinical and laboratory response.