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Hematology > Disorders of DNA Met and Bone Marrow Failure > Flashcards

Disorders of DNA Met and Bone Marrow Failure Flashcards

1
Q

Megaloblastic Anemia

A
  • Impaired DNA synthesis
  • Normal RNA synthesis
  • Megaloblastic changes noted in ALL hematopoietic lines
  • Nuclear - cytoplasmic asynchrony
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2
Q

Vitamin B12 / Folate

A
  • coverts uridine to thymidine (needed for DNA synthesis)
  • converts homocysteine to methione (needed for nervous system function)
  • converts methylmalonic acid to succinyl CoA (needed for myelin sheath formation)
  • Vit B12 keeps folate in cell via Methyl folate trap
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3
Q

Ineffective Erythropoiesis in megaloblastic anemia

A
  • Increased Pre-RBC in Bone Marrow, with decreased release into peripheral blood. (RBC so abnomal they don’t make it into the peripheral blood)
  • Intramedullary hemolysis (breaking up of RBC in bone marrow):
    • Increased serum bilirubin, LDH, and Iron
  • Ineffective granulopoiesis (giant metas and bands die prematurely in marrow)
  • Ineffective thrombopoieisis (increased abnormal megakaryotcytes (platelet precursors) in marrow + thrombocytopenia)
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4
Q

Bone marrow morphology in megaloblastic anemia

A
  • Hypercellular
  • M:E Ratio is increased (1:1)
  • Megaloblastic erythroid precursors
  • Megaloblastic WBC precursors
  • Megaloblastic megakaryocytes
  • ** Nucleus looks like salami
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5
Q

Peripheral blood morphology in megaloblastic anemia

A
  • Macrocytosis (Increased MCV)
  • Macroovalocytes
  • Pancytopenia (all cells decreased)
  • Decreased reticulocytes
  • Howell Jolly Bodies (nuclear fragment)
  • Nucleated RBC
  • Hypersegmented neutrophils (> 5)
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6
Q

Causes of megaloblastic anemia

A
  • Vitamin B12 Deficiency
  • Folic Acid Deficiency
  • Myelodysplastic Syndromes / Leukemia
  • Drug-induced: Chemotherapy, Anticonvulsants
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7
Q

Vitamin B12 Metabolism

A
  • B-12/IF complex travels down to ileum, where it binds to specific receptor.
  • In ileal cell, B12 is bound to transcobalamin II, and released into portal circulation.
  • TCII/B12 complex circulates, and is taken up by cells, where B12 is released.
  • Complex in blood is transferred to TC I.
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8
Q

Vitamin B12 Deficiency

A
  • only from animal cells
  • 2-7 year storage = daily requirement low and storage rate high
  • parietal cells (stomach) secrete IF - intrinsic factor
  • IF binds to B-12 at higher pH in duodenum
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9
Q

Causes of B12 Deficiency

Important Concept

A
  • Poor intake (rare)
  • Lack of IF production
  • Gastrectomy, Pernicious Anemia
  • B12/IF complex can’t get to terminal ileum
  • Bacterial overgrowth, tapeworm
  • Complex can’t be absorbed
  • No ileum, sprue, Crohn’s disease
  • Transcobalamin deficiency (very rare)
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10
Q

Pernicious Anemia

A
  • autoimmune disease of late middle age
  • most common cause of cobalamin deficiency
  • 2% of people over 60 have this disease
  • seen more in norther europeans and african americans
  • Can be Autosomal Recessive
  • Gastric parietal atrophy:
    • Achlorhydria, no IF production
    • Antibodies against parietal cells and IF
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11
Q

Clinical Manifestations of Pernicious Anemia

A
  • loss of appetite
  • glossitis (smooth tongue)
  • neurologic problems
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12
Q

Folate Metabolism

A
  • Folate present in green leafy vegetables.
  • Absorbed in small intestines.
  • Body has only 3-6 month store of folate.
  • Folate absorbed in small bowel, transported and stored in liver.
  • Some folate excreted in bile, then reabsorbed.
  • Alcoholism reduces reabsorption
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13
Q

Causes of Folic Acid Deficiency

Important Concept

A
  • Main cause is decreased dietary intake
  • Malabsorption (ex. Tropical sprue)
  • Increased requirement: Pregnancy, Increased hematopoiesis (growth spurt in children)
  • Drug-induced
  • *Low Vit B12 = Low RBC Folate lvls
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14
Q

Macrocytosis

Important Concept

A
  • MCV > 100 fL, but usually not > 110 fL
  • RBC appear large and round
  • Causes include:
    • increased cholesterol and/or lipid in RBC membrane
    • anemia associated with an increased reticulocyte count
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15
Q

Causes for Macrocytosis

Important Concept

A
  • Alcoholism
  • Chronic liver disease
  • Shift reticulocytosis (lots of retics = polychromasia)
  • Hypothyroidism
  • Hematologic disorders
  • Immunosuppressive drugs (AZT)
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16
Q

Aplastic Anemia

Important Concept

A
  • Disorder characterized by loss or replacement of bone marrow elements
  • May be hereditary or acquired (more common)
17
Q

Acquired Aplastic Anemia

A
  • Idiopathic - 70% of cases
  • Chemical exposure: Benzene compounds, insecticides, weed killers; May be reversible, also associated with chromosomal abnormalities
  • Drugs (Ex. Chloroamphenicol and phenylbutazone)
  • Radiation (Production of free radicals interferes with DNA production)
  • Infections (Predominantly viral)
  • Autoimmune (Usually a result of altered immune status; Pregnancy, graft vs host)
18
Q

Congenital Aplastic Anemia

A

Fanconi’s Anemia

  • Autosomal recessive
  • Associated with physical and chromosomal abnormalities
  • Patients have an increased incidence of cancer and leukemia
  • Currently, most patients are treated with allogeneic bone marrow transplant.
19
Q

Clinical Manifestations of Aplastic Anemia

A
  • Pancytopenia (overall shut down of bone marrow)
  • Fatigue, dyspnea, palpitations
  • Bleeding
  • Infection
20
Q

Laboratory Evaluation of Aplastic Anemia

A
  • Pancytopenia
  • Normochromic, normocytic anemia of varying degrees
  • Decreased reticulocyte***
  • Hypocellular marrow
21
Q

Treatment and Prognosis of Aplastic Anemia

A
  • Untreated, poor prognosis
  • 1970 - Androgen therapy to stimulate erythropoiesis (Testosterone stimulates RBC production), slowed progession of disease
  • Bone marrow transplant – 75% long term survival
  • Gene therapy – in developmental stages
22
Q

Pure Red Cell Aplasia

Important Concept

A
  • Rare
  • Selective hypoproliferation of the unipotential erythroid stem cell (still aplastic buy only effects RBCs)
  • Acquired (Acute or Chronic): About 80% have spontaneous remission
  • Congenital - Diamond-Blackfan Syndrome
23
Q

Acquired Pure Red Cell Aplasia

A
  • Viral: Temporary erythroblastopenia of childhood (TEC), Parvovirus B19
  • Subsequent to hemolytic anemias
  • Drugs and chemicals
24
Q

Chronic Pure Red Cell Aplasia

A
  • Autoimmune disorders: Lupus, Rheumatoid arthritis, Autoimmune hemolytic anemia
  • Neoplasms
  • Drugs
25
Q

Diamond-Blackfan Syndrome

A
  • Rare, congenital disorder
  • Presents from infancy to 6 years of age
  • No leukopenia or thrombocytopenia
  • Erythropoietin is normal or increased
  • Most likely problem is a molecular defect leading to decreased responsiveness to erythropoietin
  • Associated with increased incidence of AML
26
Q

Congenital Dyserythropoietic Disorders

A

CDAs

  • associated with anemia, erythroid hyperplasia, and weird/abnormal erythroid precursors (often multinucleated)
  • Type I, II (most common) and III

Hematology (20 decks)

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