Anemia: RBC Membrane and Enzyme Defects

Questions and Answers

What compensatory mechanism may fail in patients with limited cardiac reserve when experiencing anemia?

Increased plasma volume

Decreased cardiac output

Increased cardiac output (correct)

Diminished oxygen affinity of hemoglobin

Which type of anemia is characterized by a defect in hemoglobin synthesis?

Macrocytic anemia

Microcytic anemia (correct)

Normocytic anemia

Anemia due to inflammation

What effect does an increase in 2,3-diphosphoglycerate (2,3-DPG) have on hemoglobin's oxygen affinity?

It has no effect on hemoglobin.

It decreases hemoglobin's oxygen affinity. (correct)

It completely inhibits oxygen binding.

It increases hemoglobin's oxygen affinity.

In morphologic classification of anemia, what condition is classified as macrocytic?

Megaloblastic anemia due to B12 deficiency Signup and view all the answers

What is a potential cause for increased red blood cell loss in anemia?

Internal hemorrhage Signup and view all the answers

Which condition is associated with impaired red blood cell production?

Acute leukemia Signup and view all the answers

What is the result of increased plasma volume during anemia?

Decreased blood viscosity Signup and view all the answers

What type of anemia is characterized by megaloblastic macrocytic anemia caused by folate deficiency?

Megaloblastic anemia Signup and view all the answers

What is the primary consequence of anemia related to red blood cell (RBC) membrane structural defects?

Reduced oxygen-carrying capacity Signup and view all the answers

Which underlying mechanism can lead to anemia due to RBC enzyme defects?

Deficient synthesis of hemoglobin Signup and view all the answers

In terms of the structure and function of the body, anemia impacts which of the following?

Cardiovascular efficiency Signup and view all the answers

Which of the following is NOT considered a nutritional deficiency associated with anemia?

Zinc Signup and view all the answers

Which definition accurately describes anemia?

Reduction of total circulating red cell mass Signup and view all the answers

What is the primary purpose of a Complete Blood Count (CBC) in the evaluation of anemia?

To determine the presence of anemia and its underlying cause Signup and view all the answers

What is a potential clinical outcome of tissue hypoxia due to anemia?

Fatigue and weakness Signup and view all the answers

Which parameter of the Complete Blood Count measures the average volume of red blood cells?

Mean Cell Volume (MCV) Signup and view all the answers

Anemia can be characterized as which of the following disorders?

The most common disorder of blood Signup and view all the answers

Which type of anemia is associated with a myelophthisic process?

Anemia due to metastatic cancer Signup and view all the answers

Which aspect of pathology is related to an anemia diagnosis?

Altered red blood cell lifespan Signup and view all the answers

What role do RBC membrane structural defects play in the development of anemia?

They contribute to the destruction of RBCs Signup and view all the answers

Which substance is essential for erythropoiesis and can be a deficiency-related cause of anemia?

Erythropoietin Signup and view all the answers

What does the Reticulocyte count indicate in the context of anemia evaluation?

The bone marrow's capacity to produce new red blood cells Signup and view all the answers

Which of the following is a common toxin that can lead to anemia?

Lead Signup and view all the answers

Which condition is most likely to cause a lack of erythropoietin, leading to anemia?

Chronic kidney disease Signup and view all the answers

What is the primary change observed in sickle cell disease due to repeated cycles of sickling?

Permanent membrane damage of red blood cells Signup and view all the answers

Which condition can precipitate sickling in individuals with sickle cell disease?

High altitude exposure Signup and view all the answers

Which complication is most directly associated with vaso-occlusive crises in sickle cell disease?

Acute chest syndrome Signup and view all the answers

What characterizes sickle cell trait in carriers?

Rare instances of anemia except in severe conditions Signup and view all the answers

What mechanism leads to autosplenectomy in sickle cell disease?

Repeated splenic infarctions due to sludging Signup and view all the answers

Which of the following findings is typically observed in peripheral blood of sickle cell disease patients?

Presence of sickled cells and poikilocytosis Signup and view all the answers

Aplastic crisis in sickle cell disease is primarily caused by which infection?

Parvovirus B19 infection Signup and view all the answers

What is a potential consequence of autosplenectomy in sickle cell disease?

Increased risk of bacterial infections Signup and view all the answers

What leads to hemolysis in mature RBCs deficient in G6PD when exposed to oxidative stress?

The inability to synthesize G6PD Signup and view all the answers

Which of the following could NOT contribute to iron deficiency anemia?

Uncontrolled muscle metabolism Signup and view all the answers

In individuals with G6PD deficiency, which substance can potentially trigger a hemolytic event?

Naphthalene Signup and view all the answers

Which lab findings are indicative of severe iron deficiency anemia?

Decreased serum iron Signup and view all the answers

What characteristic is common among the majority of individuals with G6PD deficiency?

Remain largely asymptomatic Signup and view all the answers

Which factor does NOT contribute to iron deficiency according to common causes?

Genetic predisposition Signup and view all the answers

What is a common finding in the lab results of someone with severe iron deficiency anemia?

Decreased reticulocyte count Signup and view all the answers

Which medication is known to potentially cause hemolysis in patients with G6PD deficiency?

Dapsone Signup and view all the answers

Study Notes

Definition of Anemia

Anemia is defined as a reduction in total circulating red cell mass, leading to decreased oxygen-carrying capacity and tissue hypoxia.
Causes include decreased red blood cell count, diminished hemoglobin levels, or reduced red blood cell mass.

Physiological Compensatory Mechanisms

Increased cardiac output; patients with existing heart conditions may experience symptoms at higher hemoglobin levels.
Increased plasma volume enhances RBC efficiency by reducing viscosity.
Elevated levels of 2,3-diphosphoglycerate (2,3-DPG) decrease hemoglobin's oxygen affinity, promoting oxygen delivery to tissues.

Classification of Anemias

Morphologic:
- Microcytic: typically related to hemoglobin synthesis defects.
- Macrocytic: includes megaloblastic (B12, folate deficiencies) and non-megaloblastic types (due to alcohol, liver disease, hypothyroidism).
- Normocytic: related to inflammation, acute hemolysis, blood loss, or chronic kidney disease.
Pathophysiologic:
- Increased RBC loss: hemorrhage (external/internal) and hemolysis (immune, microangiopathic, intrinsic defects).
- Impaired red cell production: can be stem cell-related, nutritional deficiencies, toxin/drug-induced, lack of erythropoietin, or due to myelophthisic processes.

Laboratory Evaluation of Anemia

Focuses on confirming anemia and identifying its underlying cause.
Complete Blood Count (CBC) provides information including:
- Hemoglobin (g/dL): primary RBC component.
- Hematocrit (%): percentage of blood volume occupied by RBCs.
- RBC indices:
  - Mean Cell Volume (MCV): average volume of RBCs.
  - Mean Cell Hemoglobin (MCH): average mass of hemoglobin per RBC.
  - Mean Cell Hemoglobin Concentration (MCHC): average concentration of hemoglobin in packed RBC volume.
  - Red Cell Distribution Width (RDW): measures variability in RBC volume.

Sickle Cell Disease

Sickle cell disease arises from hemoglobin S (HbS); repeated sickling results in membrane damage, hemolysis, and vaso-occlusive crisis.
Factors precipitating sickling include low oxygen saturation, high altitude, acidosis, and infections.
Newborns have high HbF levels, delaying sickling until about 6-9 months.
Sickle cell trait is common among African Americans, providing malaria resistance without significant symptoms.

Complications of Sickle Cell Disease

Chronic hemolytic anemia and vaso-occlusive pain crises affecting bones, lungs, and other organs.
Aplastic crises can occur suddenly due to infections like Parvovirus B19.
Sequestration crises result from sudden splenic accumulation of RBCs, increasing infection risk due to autosplenectomy.

G6PD Deficiency

G6PD deficiency leads to vulnerability to oxidative stress, causing hemolysis during exposure to certain chemicals, medications, and foods.
Many affected individuals remain asymptomatic and face no hemolysis during steady states.

Iron Deficiency Anemia

Most common nutritional deficiency globally; driven by factors such as inadequate intake, impaired absorption, increased demand during pregnancy, and chronic blood loss.
Lab findings typically show low hemoglobin, low reticulocyte counts, low serum iron, and decreased transferrin saturation.

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Description

This quiz explores the causes and effects of anemia related to structural defects in red blood cell membranes and enzyme deficiencies. It highlights the physiological implications and the educational connections involved in understanding these conditions. Test your knowledge and comprehension of this vital topic in hematology.