T6 - RBC disorder

What is the functional definition of anemia?

Decreased oxygen carrying capacity

What is the average lifespan of a normal red blood cell?

Approximately 120 days

Which organ is the primary site of normal red blood cell destruction?

Spleen

What is the World Health Organization hemoglobin cutoff for diagnosing anemia in adult males?

< 13.0 g/dL

What is the World Health Organization hemoglobin cutoff for diagnosing anemia in non-pregnant adult females?

< 12.0 g/dL

Which nail abnormality is classically associated with severe iron deficiency anemia?

Koilonychia

How many days do normal reticulocytes spend maturing in the peripheral blood?

1 day

What is the normal range for the peripheral blood reticulocyte count?

0.5% to 2.0%

What two patient values are required to calculate the corrected reticulocyte count?

Reticulocyte percentage and hematocrit

What mean corpuscular volume (MCV) cutoff defines microcytic anemia?

< 80 fL

What mean corpuscular volume (MCV) cutoff defines macrocytic anemia?

100 fL

A patient has microcytic anemia, low serum ferritin, and high TIBC. What is the most likely diagnosis?

Iron deficiency anemia

What lab value is best used to differentiate between hyperproliferative and hypoproliferative normocytic anemias?

Reticulocyte count

The presence of hypersegmented neutrophils in a patient with macrocytic anemia indicates which broad category of anemia?

Megaloblastic anemia

Where does the vast majority of normal extravascular red blood cell destruction occur?

Spleen, bone marrow, and liver

Which type of bilirubin is characteristically elevated in the blood during excess extravascular hemolysis?

Unconjugated bilirubin

What percentage of normal red blood cell destruction occurs via intravascular hemolysis?

Approximately 10%

The presence of hemosiderin within renal epithelial cells indicates which type of hemolysis?

Intravascular hemolysis

A patient presents with anemia, jaundice, and gallstones. What is the most likely underlying mechanism?

Chronic hemolysis

Which RBC membrane protein directly anchors the spectrin cytoskeleton to the transmembrane Band 3 protein?

Ankyrin

Which RBC membrane protein complex primarily stabilizes the horizontal interactions of the spectrin cytoskeleton?

Spectrin dimer-dimer association

What is the most common inheritance pattern for Hereditary Spherocytosis?

Autosomal dominant

The loss of membrane microvesicles in Hereditary Spherocytosis directly leads to a decrease in which cellular ratio?

Surface area-to-volume ratio

Which RBC index is characteristically elevated above 36% in Hereditary Spherocytosis?

Mean corpuscular hemoglobin concentration (MCHC)

Which classic laboratory test demonstrates increased red blood cell lysis in hypotonic solutions?

Osmotic fragility test

Hereditary Elliptocytosis is primarily caused by a defect in which class of cytoskeletal interactions?

Horizontal interactions

Which severe variant of hereditary elliptocytosis is characterized by extreme thermal instability of red blood cells?

Hereditary Pyropoikilocytosis

Southeast Asian Ovalocytosis (SAO) provides mild protection against which infectious disease?

Malaria

Acanthocytes (spur cells) are most commonly associated with severe disease of which organ?

Liver

Which rare autosomal recessive disorder causes acanthocytosis due to an MTP gene mutation?

Abetalipoproteinemia

Which RBC metabolic pathway generates NADPH to protect against oxidative stress?

Pentose Phosphate Shunt

Which RBC metabolic shunt produces 2,3-diphosphoglycerate to modulate hemoglobin oxygen affinity?

Rapoport-Luebering Shunt

What is the genetic inheritance pattern of G6PD deficiency?

X-linked recessive

Name three common triggers that induce acute hemolytic crisis in patients with G6PD deficiency.

Fava beans, infections, and certain drugs

What two classic red blood cell morphologies are seen on a peripheral smear during a G6PD hemolytic crisis?

Bite cells and blister cells

What intracellular inclusion is formed by denatured hemoglobin in G6PD deficiency?

Heinz bodies

Which rapid screening test evaluates for G6PD deficiency by assessing the production of NADPH?

Fluorescent spot test

Acute hemolytic transfusion reactions are most commonly caused by incompatibility in which blood group system?

ABO blood group

Hemolytic disease of the newborn (HDN) is most classically caused by maternal IgG antibodies directed against which fetal antigen?

Rh antigen

Which maternal antibody isotype can cross the placenta and cause hemolytic disease of the newborn?

IgG

Warm Autoimmune Hemolytic Anemia (AIHA) is typically mediated by which immunoglobulin isotype?

IgG

In Warm AIHA, IgG-coated red blood cells are prematurely sequestered and destroyed in which organ?

Spleen

In Cold AIHA, IgM antibodies react with RBCs at low temperatures and activate which protein system to cause hemolysis?

Complement system

A patient with Cold AIHA develops marked pallor of the fingers upon exposure to cold temperatures. What is this phenomenon called?

Raynaud's Phenomenon

Which laboratory test detects antibodies or complement bound to a patient's red blood cells in vivo?

Direct Antiglobulin Test (DAT)

Which laboratory test detects antibodies circulating in the serum that can react with red blood cell antigens in vitro?

Indirect Antiglobulin Test (IAT)

Which antibiotic classically causes immune hemolytic anemia via the drug adsorption mechanism?

Penicillin

A patient receives a cephalosporin and develops immune hemolytic anemia. Which mechanism is most likely responsible?

Drug adsorption mechanism

Which classic antiarrhythmic drug causes immune hemolytic anemia via the immune complex (innocent bystander) mechanism?

Quinidine

Which antihypertensive drug classically causes immune hemolytic anemia by inducing true autoantibodies against RBC antigens?

Methyldopa

Which fragmented red blood cell shape is the hallmark of Microangiopathic Hemolytic Anemia (MAHA)?

Schistocytes

Paroxysmal Nocturnal Hemoglobinuria (PNH) is caused by a lack of which class of cell-surface anchoring proteins?

GPI-anchored proteins

Which two specific GPI-anchored proteins are absent on RBCs in Paroxysmal Nocturnal Hemoglobinuria?

CD55 (DAF) and CD59 (MIRL)

A patient presents with pancytopenia, fatigue, and dark "coca-cola-colored" urine in the morning. What is the most likely diagnosis?

Paroxysmal Nocturnal Hemoglobinuria (PNH)

What diagnostic test evaluates for Paroxysmal Nocturnal Hemoglobinuria by utilizing acidified serum?

Acidified serum test (Ham's test)

Which flow cytometry reagent binds directly to GPI anchors and is the gold standard for confirming PNH?

FLAER (Fluorescent-labeled proaerolysin)

What is the most common cause of Iron Deficiency Anemia in adult populations?

Blood loss

Spoon-shaped nails and angular stomatitis are classic physical findings of which anemia?

Iron deficiency anemia

In the three stages of iron deficiency, which laboratory value is the first to become abnormally low?

Serum ferritin

Congenital sideroblastic anemia is most commonly caused by an X-linked mutation in which gene?

ALAS gene

What distinctive inclusion bodies are seen in red blood cells on a peripheral smear in sideroblastic anemia?

Pappenheimer bodies

In Anemia of Chronic Disease, what is the expected level of serum ferritin?

Normal or increased

In Anemia of Chronic Disease, what is the expected level of Total Iron Binding Capacity (TIBC)?

Normal or low

Megaloblastic anemia is primarily caused by impairment of which cellular process?

DNA synthesis

Pernicious anemia causes Vitamin B12 deficiency through autoimmune destruction of which gastric cells?

Parietal cells

Deficiency of which gastric secretion directly leads to impaired absorption of Vitamin B12 in pernicious anemia?

Gastric acid and intrinsic factor

Which tapeworm infection is a known cause of Vitamin B12 deficiency?

Fish tapeworm

What is the most common cause of folic acid deficiency?

Decreased intake (malnutrition)

Which chemotherapeutic drug causes megaloblastic anemia by inhibiting dihydrofolate reductase?

Methotrexate

Atrophic glossitis and severe neurological complications specifically indicate a deficiency in which vitamin?

Vitamin B12

The presence of macro-ovalocytes and which type of white blood cell are classic peripheral smear findings in megaloblastic anemia?

Hypersegmented neutrophils

Which two metabolic markers are elevated in the plasma and urine of patients with Vitamin B12 deficiency?

Homocysteine and methylmalonic acid

A patient presenting with peripheral pancytopenia and a hypocellular bone marrow is suffering from which general syndrome?

Bone marrow failure syndrome

Infection with which parvovirus is a well-known infectious cause of aplastic anemia and pure red cell aplasia?

Parvovirus B19