Hematopoietic System Case Studies

A set of flashcards to review key concepts related to the hematopoietic system and its associated disorders for upcoming exams.

What is hematopoiesis?

Hematopoiesis is blood cell production.

What are the two significant pathways to generate various types of leukocytes?

Myelopoiesis and Lymphopoiesis.

What cell type do hematopoietic stem cells (HSCs) develop into during hematopoiesis?

Precursor cells or 'blast' cells.

What is erythropoiesis?

Erythropoiesis is the process of red blood cell production.

What is the primary site of hematopoiesis in adults?

Bone marrow.

What is thrombopoiesis?

Thrombopoiesis is the process of platelet production.

What is the function of erythropoietin (EPO)?

EPO stimulates the production and maturation of red blood cells.

What does SCID stand for and what does it result from?

Severe Combined Immunodeficiency; it results from a lack of production of B cells and T cells.

What is aplastic anemia characterized by?

Aplastic anemia is characterized by pancytopenia, which is a reduction in red blood cells, white blood cells, and platelets.

What is the main risk factor for infection in neutropenic patients?

An absolute neutrophil count (ANC) of less than 1,000 cells/mm3.

How is anemia defined by the WHO?

Anemia is defined as hemoglobin (Hb) < 13 g/dL in men or < 12 g/dL in women.

What is the leading cause of anemia worldwide?

Iron deficiency.

What is a normal survival time for erythrocytes?

120 days.

What is the significance of reticulocyte count in anemia?

It reflects how quickly immature RBCs are produced by the bone marrow.

What laboratory finding is expected in iron deficiency anemia?

Decreased ferritin levels.

What are the clinical symptoms of anemia?

Chest pain, fatigue, dizziness, shortness of breath.

What causes macrocytic anemia?

Abnormal DNA metabolism due to vitamin B12 or folate deficiency.

What does a high reticulocyte count indicate?

It may indicate acute blood loss or hemolysis.

What findings are associated with vitamin B12 deficiency anemia?

Decreased vitamin B12 levels, increased mean corpuscular volume (MCV), and increased homocysteine.

What is hematopoiesis and what cells does it develop?

Hematopoiesis is the process of blood cell production, where hematopoietic stem cells develop into precursor or 'blast' cells. It develops red blood cells, white blood cells (leukocytes), and platelets.

Compare erythroblasts, reticulocytes, and mature red blood cells:

• Erythroblast: Nucleated precursor cells in bone marrow, synthesizing hemoglobin.

• Reticulocyte: Immature red blood cell, lacks a nucleus but contains ribosomal RNA; released into the bloodstream and matures within 1-2 days. Its count reflects bone marrow production.

• Mature Red Blood Cell (Erythrocyte): Biconcave, anucleated cell, transports oxygen with a 120-day survival time.

What types of blood cells are developed by Leukopoiesis?

Leukopoiesis generates various types of leukocytes (white blood cells), including neutrophils, eosinophils, basophils, monocytes (which mature into macrophages), and lymphocytes (T cells and B cells).

What cells are developed by Thrombopoiesis?

Thrombopoiesis is the process of platelet production.

Compare erythropoiesis during fetal development and in adults:

• Fetal Development: Initially occurs in the yolk sac, then shifts to the liver and spleen, and eventually to the bone marrow.
• Adults: Primarily occurs in the bone marrow.

Define aplastic anemia and state its signs/symptoms.

Aplastic anemia is characterized by pancytopenia (a reduction in red blood cells, white blood cells, and platelets).

Signs/Symptoms:

• Anemia (low RBCs): Chest pain, fatigue, dizziness, shortness of breath.
• Leukopenia (low WBCs/neutrophils): Increased risk of infections.
• Thrombocytopenia (low platelets): Bleeding or bruising tendencies.

Describe the role of EPO, iron, folate, and Vitamin B12 in red blood cell maturation and development:

• Erythropoietin (EPO): Stimulates the production and maturation of red blood cells.
• Iron: Essential component of hemoglobin; critical for hemoglobin synthesis.
• Folate (Vitamin B9) & Vitamin B12 (Cobalamin): Vital cofactors for DNA synthesis and cell division; deficiencies lead to macrocytic anemia due to impaired RBC precursor maturation.

Define febrile neutropenia.

Febrile neutropenia is a fever (\ge 38.3^{\circ} C single or \ge 38.0^{\circ} C sustained for > 1 hour) in a patient with neutropenia (absolute neutrophil count (ANC) < 1,000 cells/mm3, or expected to fall below 500 cells/mm3). The main risk factor for infection is this low ANC.

Compare microcytic (iron deficiency) anemia vs. macrocytic (vitamin B12/folate deficiency) anemia, including key laboratory findings (Hb, reticulocytes, MCV, ferritin, serum iron, transferrin saturation, TIBC, B12/folate levels, homocysteine, MMA).

Microcytic (Iron Deficiency) Anemia:

• Cause: Insufficient iron for hemoglobin synthesis.
• MCV: Decreased (< 80 fL).
• Hemoglobin (Hb): Decreased.
• Reticulocyte Count: Low.
• Ferritin: Decreased.
• Serum Iron: Decreased.
• Transferrin Saturation: Decreased.
• Total Iron Binding Capacity (TIBC): Increased.
• Vitamin B12/Folate Levels: Normal.
• Homocysteine: Normal.
• MMA: Normal.

Macrocytic (Vitamin B12/Folate Deficiency) Anemia:

• Cause: Impaired DNA synthesis due to vitamin B12 or folate deficiency.
• MCV: Increased (> 100 fL).
• Hemoglobin (Hb): Decreased.
• Reticulocyte Count: Low.
• Ferritin: Normal to increased.
• Serum Iron: Normal to increased.
• Transferrin Saturation: Normal to increased.
• Total Iron Binding Capacity (TIBC): Normal.
• Vitamin B12 Levels: Decreased (in B12 deficiency).
• Folate Levels: Decreased (in folate deficiency).
• Homocysteine: Increased (in both B12 and folate deficiency).
• MMA: Increased (specific to B12 deficiency; normal in folate deficiency).

How are key laboratory evaluations like Hemoglobin, Reticulocyte Count, MCV, Ferritin, Serum Iron, Transferrin Saturation, TIBC, Vitamin B12/Folate Levels, Homocysteine, and MMA interpreted?

• Hemoglobin (Hb): Indicator of anemia severity. Low levels indicate anemia.
• Reticulocyte Count: Reflects bone marrow's RBC production rate. Low in production issues, high in loss/destruction.
• Mean Corpuscular Volume (MCV): Classifies anemia as microcytic (low), normocytic (normal), or macrocytic (high).
• Ferritin: Reflects iron stores; most sensitive for iron deficiency.
• Serum Iron: Amount of iron bound to transferrin in blood.
• Transferrin Saturation: Percentage of transferrin saturated with iron.
• Total Iron Binding Capacity (TIBC): Measures available iron binding sites, often inverse to iron stores.
• Vitamin B12 and Folate Levels: Direct measurement for deficiencies.
• Homocysteine: Elevated in both B12 or folate deficiency.
• Methylmalonic Acid (MMA): Elevated in B12 deficiency; normal in folate deficiency.