Red Blood Cell and Bleeding Disorders Flashcards
Characterized by defective red cell membrane proteins spectrin and ankyrin; on PBS, red cells are spherical which lack central pallor, and they show increased osmotic fragility when placed in hypotonic salt solutions; anemia with characteristically increased MCHC.
Hereditary spherocytosis (Intrinsic; extravascular)
X-linked disorder in which red cells are unusually susceptible to damage cause by oxidants. (Drugs that produce oxidants include antimalarials, sulfonamides, nitrofurantoin, phenacetin, and vitamin K derivatives); Heinz bodies (derived from hemoglobin) seen on PBS of splenectomized patients; Bite cells seen on PBS of patients with intact spleen function.
Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency) (Intrinsic; extravascular and intravascular)
This results from substitution of valine for glutamic acid at the 6th position of the b-chain, producing HbS; bizarre, elongated, spindled or boat-shaped cells on PBS (evident on low oxygen tension states); clinically, prominent cheekbones and changes in skull resembling a crew-cut skull x-ray, due to bone marrow expansion; also with painful vaso-occlusive crisis; spleen may be enlarged, but in chronic cases may be small and fibrosed (autosplenectomy), rendering them susceptible to infections with encapsulated bacteria; treatment is Hydroxyurea that increases HbF.
Sickle cell anemia (Intrinsic; extravascular)
Microcytic, hypochromic anemias characterized by deficiency of either a- or b-globin chains (memory device: the name is what it lacks).
Thalassemia (Intrinsic; extravascular)
Condition caused by deletion of 1 a- globin gene.
Silent carrier
Condition caused by deletion of 2 a- globin genes; symptomatic at birth because of deficiency in HbF.
a-Thalassemia
Disease caused by deletion of 3 a-genes.
Hemoglobin H disease
Condition caused by deletion of all four a-globin genes.
Hydrops fetalis
In b-Thalassemia, an individual who inherits one abnormal allele (out of 2) has this asymptomatic to mildly symptomatic condition; Red cells with a central, dark-red puddle due to collection of hemoglobin (target cells) on PBS.
b-Thalassemia minor
Individuals with b-Thalassemia who inherit two abnormal alleles, with severe anemia requiring regular blood transfusions; usually symptomatic at around six months of age because HbF synthesis ceases at this time; marked hypochromia, poikilocytosis (variation in cell size) and anisocytosis (variation in cell shape) with normoblasts (signifying erythropoietic drive).
b-Thalassemia major (Cooley anemia)
A mutation in the gene pigA causes this disease; there is deficiency of PIG (phosphatidylinositol glycan) that anchors CD55 and CD59 to the red cell surface; without such, red cells become susceptible to complement-mediated lysis.
Paroxysmal nocturnal hemoglobinuria (Intrinsic; intravascular)
Anemia caused by low-affinity IgM which bind to red cell membranes only at temp <30 degC, commonly experienced by distal parts of the body; associated with Mycoplasma pneumoniae, and EBV infections.
Cold antibody immune-hemolytic anemia (Extrinsic; intravascular)
Hemolysis caused by IgG or IgA antibodies that are active at 37 deg C, which results in opsonization of red cells by the autoantibodies.
Warm antibody immune-hemolytic anemia (Extrinsic; intravascular)
Anemia observed in a variety of pathologic states, in which small vessels become particularly obstructed (e.g. DIC, malignant HTN, SLE, etc.); schistocytes, Burr cells, helmet cells, triangle cells are seen in this condition.
Microangiopathic hemolytic anemia (Extrinsic; intravascular)
Most common cause of anemia in both developing and developed countries; microcytic, hypochromic with low ferritin, low serum iron levels low transferrin saturation, and increased TIBC.
Iron deficiency anemia
Most common cause of anemia in hospitalized patients; anemia characterized by high levels of hepcidin, responsible for blocking the transfer of iron to erythroid precursors, hence causing anemia; normocytic, normochromic but can be microcytic, hypochromic; increased ferritin, low serum iron levels, low transferrin saturation, and decreased TIBC.
Anemia of chronic disease
Anemia characterized by hypercellular marrow as a result of increased number of megaloblasts, which are large cells that have delicate, finely reticulated nuclear chromatin and abundant basophilic cytoplasm; can be caused by Folate (without neurologic symptoms) or Cobalamin (with neurologic symptoms) deficiency; PBS findings include: hypersegmented neutrophils, large, egg-shaped macro-ovalocytes.
Megaloblastic anemia
Bone marrow is markedly hypocellular, with >90% of the intertrabecular space being occupied by fat; normocytic, normochromic; most commonly caused by chemicals (Benzene) and drugs (Chloramphenicol).
Aplastic anemia
Selective suppression of marrow erythroid precursors; can be autoimmune or infectious (Parvovirus) in etiology; presents with normocytic, normochromic anemia with virtuallyt absent eryhtroblasts in bone marrow, and normal granulo- and thrombopoietic elements; paraneoplastic syndrome of thymoma.
Pure red cell aplasia (PRCA)
Anemia caused by replacement of the bone marrow by in infiltrative processes such as metastatic carcinoma and granulomatous disease; leads to the appearance of early erythroid and granulocytic precursors (leukoerythroblastosis) and teardrop-shaped red cells (dacrocytes) in the peripheral blood.
Myelophthisic anemia
Denotes an increase in red cells per unit volume of peripheral blood, usually in association with an increase in hemoglobin concentration; maybe relative (hemoconcentration) or absolute; absolute may be primary (polycythemia vera) or secondary (increased erythropoietin, lung disease, high altitude, endurance athletes or erythropoietin-secreting tumors).
Polycythemia
Caused by a systemic activation of coagulation pathways, leading to formation of thrombi throughout the microcirculation, and subsequent bleeding due to consumption of coagulation factors; laboratory findings include: thrombocytopenia, increased bleeding time and prolonged PT and PTT.
Disseminated intravascular coagulation (DIC)
Caused by antiplatelet antibodies directed against glycoproteins IIb-IIIa, Ib-IX (usually IgG); laboratory findings include: decreased platelet count, prolonged bleeding time, and normal PT and PTT.
Immune thrombocytopenia/Immune thrombocytopenic purpura (ITP)
Form of ITP usually affecting adults and females more than males; associated with SLE, HIV, B-cell neoplasms (CLL); glucocorticoids are indicated; other tretament modalities include, splenectomy, rituximab (anti CD20) in B-cell neoplasms, and TPO-mimetic (Romiplostim).
Chronic ITP
Form of ITP usually affecting children; common antecedent viral illness; glucocorticoids are indicated only when severe; usually self-limited.
Acute ITP
Thrombocytopenia with thrombosis, in a patient taking anticogulants raises suspicion of the this disorder.
Heparin-induced thrombocytopenia (HIT)
Most common hematologic manifestation of HIV infection.
Thrombocytopenia
Associated with pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, transient neurologic deficits and renal failure; primary defect is deficiency of ADAMTS13, a vWF metalloproteinase; laboratory findings include: decreased platelet count, prolonged bleeding time, and normal PT and PTT.
Thrombotic thrombocytopenic purpura (TTP)
Associated with childhood onset microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure; no neurologic symptoms; often with a history of bloody diarrhea (E. coli O157:H7 infection); with normal ADAMTS13 activity; laboratory findings include: decreased platelet count, prolonged bleeding time, and normal PT and PTT.
Hemolytic Uremic Syndrome (HUS)
Decreased gp Ib leads to defective platelet adhesion; laboratory findings include: decreased platelet count, prolonged bleeding time, and normal PT and PTT.
Bernard-Soulier syndrome
Decreased gp IIb-IIIa leads to defective platelet aggregation, laboratory findings include: normal platelet count, prolonged bleeding time, and normal PT and PTT.
Glanzmann thrombasthenia
Most common inherited bleeding disorder; most common presenting symptoms of this condition are spontaneous bleeding from mucous membranes, excessive bleeding from wounds, or menorrhagia; bleeding tendency often goes unnoticed until some hemostatic stress, such as surgery, reveals its presence; laboratory findings include normal platelet count, prolonged bleeding time, and normal PT and prolonged PTT.
Von Willebrand disease (vWD)
Patient with this disease has a tendency toward easy bruising and massive hemorrhage after trauma or operative procedures, and recurrent bleeding into the joints; laboratory findings include normal platelet count, bleeding time, PT and prolonged PTT.
Hemophilia (Hemophilia A Factor VIII deficiency; Hemophilia B (Christmas disease) Factor IX deficiency
Vitamin K dependent coagulation and fibrinolytic factors, and laboratory picture of Vitamin K deficiency.
Factors II, VII, IX, and X; Protein C and S; normal platelet count and bleeding time; prolonged PT and PTT
Transfusion reaction to watch out for in patients with IgA deficiency.
Allergic reactions
IgM-mediated destruction of donor red cells.
Acute hemolytic transfusion reaction (AHTR)
IgG-mediated destruction of donor red cells in a previously-sensitized individual.
Delayed hemolytic transfusion reaction (DHTR)
ARDS-like complication in patients who underwent transfusion; due to activation of PMNs in lung vasculature.
Transfusion related acute lung injury (TRALI)
