Red Blood Cell Disorder Cheat Sheet

Anemia, a reduction in red blood cell mass, presents with hypoxia symptoms and is classified by MCV. Microcytic anemias stem from hemoglobin synthesis defects, while macrocytic anemias often involve DNA synthesis issues. Normocytic anemias result from destruction or underproduction, with reticulocyte count being key for diagnosis.

Core Principles

• Anemia: Reduced RBC mass, leading to hypoxia symptoms (fatigue, dyspnea, pallor).
• Diagnosis relies on Hb, Hct, and RBC count.
• MCV classification: Microcytic (<80 fL), Normocytic (80-100 fL), Macrocytic (>100 fL).
• Microcytic anemias: Defective hemoglobin (heme/globin) production.
• Macrocytic anemias: Impaired DNA synthesis (folate/B12 deficiency) or other causes.
• Normocytic anemias: Increased destruction (hemolysis) or decreased production.
• Reticulocyte count is crucial for differentiating hemolysis vs. underproduction.

Action Steps

• Assess patient for hypoxia symptoms (fatigue, dyspnea, headache).
• Measure Hb, Hct, and RBC count to confirm anemia.
• Determine MCV to classify anemia (microcytic, normocytic, macrocytic).
• Evaluate reticulocyte count to distinguish hemolysis from underproduction.
• Order specific tests based on MCV and reticulocyte count (e.g., iron studies, B12/folate levels, Coombs test).

Formulas

• Anemia Definition (Hb): Males < 13.5 g/dL, Females < 12.5 g/dL
• Corrected Reticulocyte Count = Reticulocyte Count * (Hct / 45)

Key Terms

• Anemia: Reduction in circulating red blood cell (RBC) mass.
• Hypoxia: State of oxygen deficiency, presenting as weakness, fatigue, dyspnea.
• MCV: Mean Corpuscular Volume; measures average RBC size.
• Microcytic: Anemia with MCV < 80 fL, due to defective hemoglobin synthesis.
• Normocytic: Anemia with MCV 80-100 fL, due to hemolysis or underproduction.
• Macrocytic: Anemia with MCV > 100 fL, often due to folate/B12 deficiency.
• Reticulocyte Count: Percentage of young RBCs; indicates bone marrow response.
• Hemolysis: Premature destruction of RBCs.
• Megaloblastic Anemia: Macrocytic anemia due to impaired DNA synthesis (folate/B12 deficiency).
• Pernicious Anemia: Vitamin B12 deficiency due to autoimmune destruction of parietal cells.
• Sideroblasts: RBC precursors with iron-laden mitochondria (ringed sideroblasts).
• Thalassemia: Inherited disorder of decreased globin chain synthesis.
• HbS: Hemoglobin S; causes sickle cell anemia when deoxygenated.
• HbC: Hemoglobin C; causes mild anemia with characteristic crystals.
• PNH: Paroxysmal Nocturnal Hemoglobinuria; complement-mediated RBC lysis.
• G6PD Deficiency: Enzyme deficiency leading to oxidative stress and hemolysis.
• IHA: Immune Hemolytic Anemia; antibody-mediated RBC destruction.
• MAHA: Microangiopathic Hemolytic Anemia; RBC fragmentation in small vessels.

Real World Examples

• A patient presents with extreme fatigue, pale skin, and shortness of breath after significant blood loss.: This suggests iron deficiency anemia due to blood loss, requiring iron supplementation and investigation into the source of bleeding.
• An elderly patient with a chronic inflammatory condition develops anemia.: This is likely Anemia of Chronic Disease, managed by treating the underlying inflammation and potentially using EPO.
• A child of African descent is diagnosed with severe anemia, bone deformities, and recurrent pain crises.: This points to Sickle Cell Disease, requiring chronic transfusions, hydroxyurea, and infection prophylaxis.
• A patient on methotrexate therapy develops anemia.: This could be folate deficiency due to the drug's mechanism, requiring folate supplementation.
• A patient experiences sudden onset of dark urine and fatigue after eating fava beans.: This is highly suggestive of G6PD deficiency with oxidative stress-induced hemolysis.

Timeline

• Early Life: Iron deficiency can occur in infants due to low iron in breast milk or poor diet in children.
• Young Adulthood (20-50): Iron deficiency common due to peptic ulcers (males), menorrhagia, or pregnancy (females).
• Elderly: Iron deficiency can be caused by colon polyps/carcinoma (Western) or hookworm (developing world).
• Chronic Illness: Anemia of Chronic Disease develops due to inflammation, impacting iron availability.
• Genetic Predisposition: Thalassemia and Sickle Cell Anemia are inherited disorders affecting hemoglobin synthesis or structure.
• Medication Side Effects: Certain drugs (e.g., isoniazid, methotrexate) can cause sideroblastic or folate deficiency anemia.
• Autoimmune Conditions: Pernicious anemia (B12 deficiency) and Immune Hemolytic Anemia are linked to autoimmune processes.

People

• Unknown: Patients presenting with anemia symptoms like weakness, fatigue, dyspnea.
• Unknown: Individuals with nutritional deficiencies (iron, folate, B12).
• Unknown: Patients with chronic inflammatory or malignant diseases.
• Unknown: Individuals with genetic predispositions (thalassemia, sickle cell).
• Unknown: Patients with autoimmune disorders affecting hematopoiesis.

Quiz

• Which of the following is NOT a cause of microcytic anemia?: Vitamin B12 Deficiency
• A low corrected reticulocyte count in a patient with anemia suggests:: Bone marrow underproduction
• Pernicious anemia is most commonly caused by:: Autoimmune destruction of parietal cells
• Which condition is characterized by RBCs that sickle under deoxygenated conditions?: Sickle Cell Anemia
• A patient presents with dark urine and back pain after taking certain medications. This could indicate:: G6PD deficiency