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HEMA 1: LEC > Anemias Caused by Defects of DNA Metabolism > Flashcards

Anemias Caused by Defects of DNA Metabolism Flashcards

1
Q

= causes systemic effects by impairing production of all rapidly dividing cells of the body

A

Impaired DNA

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2
Q

rapidly dividing cells of the body

A

• Cells of skin

• Epithelium of Gl tract

• Hematopoietic tissue

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3
Q

• Impaired DNA

• Hematologic effect =________

• Hallmark of the disease affecting DNA metabolism

A

MEGALOBLASTIC ANEMIA

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4
Q

Megaloblastic anemia

ROOT CAUSE:

A

impaired DNA synthesis

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5
Q

Effects of megaloblastic anemia

in bone marrow and cell division

A

• Very large cells of the bone marrow
• Reduction in the number of cell divisions

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6
Q

MA

T or F

One example of macrocytic anemia

A

True

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7
Q

VITAMIN B12 (aka)

A

COBALAMIN

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8
Q

VITAMIN B12 (COBALAMIN)
• Essential nutrient consisting of a_____

• Containing cobalt that is attached to___

A

tetrapyrrole (corrin) ring

5,6-dimethylbenzimidazolyl ribonucleotide

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9
Q

Vit B12 (Cobalamin)

• VARIOUS ANALOGS: 5

A

Hydroxycobalamin

Cyanocobalamin

coenzyme form

methylcobalamin

5’-deoxyadenosylcobalamin

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10
Q

Physiologic Roles of Vitamin B12

2 biochemical reaction:

A
  1. Isomerization of methylmalonyl coenzyme A (CoA) to succinyl CoA
  2. Transfer of a methyl group from 5-methyltetrahydrofolate (5-methyl THF) to Homocysteine = generates methionine
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11
Q

absense of Vitamim B12= impaired activity of methylmalonyl CoA mutase leads to a high level of serum_____

A

methylmalonic acid (MMA).

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12
Q

• General term used for any form of the vitamin folic acid.

A

FOLATE

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13
Q

• General term used for any form of the vitamin folic acid.

A

FOLATE

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14
Q

FOLATE

• Consist of a_____ ring attached to ________ with one or more glutamate residues.

A

pteridine ring
para-aminobenzoate

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15
Q
  • synthetic form of folate in supplements and fortified food
A

FOLIC ACID

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16
Q

• Folate circulates in the blood is predominantly as ______

A

5-Methyltetrahydrofolate (5-MTHF)

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17
Q

• FUNCTION:
1. Transfer carbon units in the form of methyl groups from donors to receptors.
2. Plays an important role in the metabolism of amino acids and nucleotides.

A

Folate

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18
Q

• Deficiency of vitamin = leads to impaired cell replication and other metabolic alterations

A

Folate

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19
Q

DEFICIENT VITAMIN B12 & FOLATE =___________ is impaired

A

THYMIDINE nucleotide production for DNA synthesis is IMPAIRED

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20
Q

Explain what happens when ther eis no thymidine nucleotide production

A

THYMIDINE(deminished) = URIDINE incorporated to DNA =>

BREAKS TO FRAGMENTATION OF DNA =>

DNA unfunctional =>

DNA replication is INCOMPLETE
=>

CELL DIVISION IS HALTED =>

LYSIS/ APOPTOSIS

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21
Q

T or F

• FOLATE DEFICIENCY- indirect effect

• VITAMIN B12 DEFICIENCY- direct effect

A

FALSE

• FOLATE DEFICIENCY- direct effect
• VITAMIN B12 DEFICIENCY- indirect effect

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22
Q

FOLATE DEFICIENCY- direct effect

A

Preventing the methylation of dUMP - deoxyuridine monophosphate (dUMP)

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23
Q

• VITAMIN B12 DEFICIENCY- indirect effect

A

The conversion of 5-methyl THF to THF is disrupted, causing 5-methyl THF to accumulate.

This accumulation is termed the “folate trap,” as folate is metabolically trapped in its 5-methyl THF form and cannot be converted to other forms of THF needed for DNA synthesis and cell division.

As a result:
Homocysteine levels increase because it cannot be converted to methionine without the involvement of vitamin B12.

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24
Q

T or F and WHY?

• RNA - is not affected by vitamin B12 or Folate deficiency

A

True!

RNA synthesis is not affected by vitamin B12 or folate deficiency because RNA synthesis relies on uridine (U) rather than thymidine (T), which is specific to DNA.

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25
Q

Other causes of Megaloblastosis

A
  1. Dysplastic erythroid precursors in myelodyplastic syndrome (MDS)
  2. Congenital dyserythropoietic anemia (CDA) types I and III
  3. Acute erythroid leukemia (FAB M6)
  4. Reverse Transcriptase Inhibitors (treatment for HIV infection)
26
Q

Systemic Manifestation of Folate and Vitamin B12 deficiency

General Symptoms:

A

fatigue, weakness, and shortness of breath

27
Q

Systemic Manifestation of Folate and Vitamin B12 deficiency

Vitamin B12:

A

• Neurologic symptoms
• Neurophyschiatric symptoms

28
Q

Systemic Manifestation of Folate and Vitamin B12 deficiency

Folate:

A

• Cardiovascular Disease
• Can cause neural tube defect (spina bifida)

29
Q

VITAMIN DEFICIENCIES
FOLATE DEFICIENCY

A

INADEQUATE INTAKE => DUE TO POOR DIET

30
Q

• FOLATE:
• Synthesized by microorganisms and higher plants.
• Ubiquitous in foods

• Good source of folate:

A

• Leafy vegetables
• Dried beans
• Liver
• Beef
• Fortified breakfast cereals
• Oranges

31
Q

VITAMIN DEFICIENCIES
FOLATE DEFICIENCY

> INCREASE NEED

A
  1. DURING PREGNANCY
  2. LACTATION
32
Q

VITAMIN DEFICIENCIES
FOLATE DEFICIENCY
> IMPAIRED ABSORPTION:
• Folate must be hydrolyzed in the____ before absorption to_____

___% = available for absorption

A

gut

small intestine

50%

33
Q

Rare autosomal recessive deficiency of a folate transporter protein (PCFT)
• Severely decreases intestinal absorption of folate.

A

proton-coupled folate transporter (PCFT)

PCFT is crucial for absorbing folate from the intestine into the bloodstream.

When this transporter is deficient, the body cannot absorb enough folate, leading to low folate levels even if dietary intake is sufficient.

34
Q

Intestinal Disease that causes folate deficiency

A

SPRUE & CELIAC DISEAE

35
Q

due to an overgrowth of bacteria or other pathogens in the intestines.

These pathogens damage the intestinal lining, reducing the body’s ability to absorb nutrients, including folate and vitamin B12.

A

Tropical Sprue

36
Q

is an autoimmune reaction to gluten (a protein found in wheat, barley, and rye).

INTOLERANCE TO GLUTEN

In people with this disease, consuming gluten triggers an immune response that damages the lining of the small intestine, impairing nutrient absorption.

This damage also leads to folate deficiency, as the body cannot absorb folate efficiently.

A

Celiac Disease (Nontropical Sprue)

37
Q

VITAMIN DEFICIENCIES
FOLATE DEFICIENCY
> IMPAIRED ABSORPTION:

A
  1. Rare autosomal recessive deficiency
  2. Intestinal Disease (SPRUE & CELIAC DISEAE)
  3. Surgical resection
  4. Inflammatory bowel disease
38
Q

VITAMIN DEFICIENCIES
FOLATE DEFICIENCY
> IMPAIRED USE OF FOLATE:

A

• Numerous drugs decrease absorption of folic acid or impair folate metabolism

• Antineoplasic, Antibaterial and Antiseizure agents, Anticancer drug

39
Q

VITAMIN DEFICIENCIES
FOLATE DEFICIENCY
EXCESSIVE LOSS OF FOLATE:
• Physiologic loss of folate occurs through_____
• Small and cannot cause deficiency

RENAL DIALYSIS
• LOSE FOLATE IN THE___
• Supplemental_____ is routinely provided

A

kidney

DIALYSATE; folic acid

40
Q

• Rare
• Possible: Strict Vegetarian (Vegans)

A

INADEQUATE INTAKE

41
Q

Strict Vegetarian (Vegans) deficient in

A

Vit b12

42
Q

Best Source of b12

A

Animal product such as liver, dairy products, fish, shellfish and eggs

43
Q

T or F

• B12 not destroyed by cooking

A

True

44
Q

VITAMIN B12 DEFICIENCY
> INCREASE NEED

A
  1. DURING PREGNANCY:
  2. LACTATION
  3. GROWTH
45
Q

VITAMIN B12 DEFICIENCY

  • IMPAIRED ABSORPTION
    • It is released from food proteins primarily in the acid environment of the…
A

stomach (PEPSIN)

46
Q

B12

• Bound by a salivary protein,____ (AKA:______)

A

haptocorrin

R Protein or Transcobalamin I

47
Q

B12

• PLASMA =___to___ bound to______

70% bound to________

A

10% to 30%
trasncobalamin

transcobalamin I and Ill (Haptocorrin)

48
Q

= Holotrasncobalamin (holoTC)

A

• Vitamib B12 + Transcobalamin complex

49
Q

• Vitamib B12 + Transcobalamin complex =

A

Holotrasncobalamin (holoTC)

50
Q

• Metabolically active form of Vitamin B12
• Binds to specific receptor in the surfaces of many different cells by endocytosis and subsequent release of of Vitamin B12 from the carrier

A

Holotrasncobalamin (holoTC)

51
Q

2 organs??? : Reserved absorbed vitamin B12

A
  • KIDNEY AND HEPATOCYTES
52
Q

VITAMIN B12 DEFICIENCY
> IMPAIRED ABSORPTION

A
  1. Failure to separate vitamin B12 from food protein in the stomach
  2. Failure to separate vitamin B12 from haptocorrin in the intestine
53
Q

VITAMIN B12 DEFICIENCY
> IMPAIRED ABSORPTION

A
  1. Failure to separate vitamin B12 from food protein in the stomach
  2. Failure to separate vitamin B12 from haptocorrin in the intestine
  3. Lack of Intrinsic factor (Pernicious Anemia),
  4. Malabsorption
  5. Competition for available vitamin B12
54
Q

Failure to separate vitamin B12 from food protein in the stomach

• Food cobalamin malabsorption =______
• Reduced gastric acidity (increasing age)
• Atrophy of stomach lining
• Gastric bypass surgery
• Long-term use of histamine type 2 receptor blockers
• Proton pumps inhibitors

A

hypochlorhydria

55
Q

Failure to separate vitamin B12 from haptocorrin in the intestine

• Chronic Pancreatic Disease Lack of_____ or _____

A

gastric acidity or lack or trypsin

56
Q

IMPAIRED ABSORPTION
- Absorption of Vitamin B12 can be impaired by

  1. Lack of Intrinsic factor (_____)
A

Pernicious Anemia

57
Q

IMPAIRED ABSORPTION
- Absorption of Vitamin B12 can be impaired by

  1. Malabsorption
    • 3.
A

Celiac disease, tropical sprue and inflammatory bowel disease

58
Q

IMPAIRED ABSORPTION
- Absorption of Vitamin B12 can be impaired by

Competition for available vitamin B12
•_______
• Able to split vitamin B12 from intrinsic factor
•______
• Intestines that are stenotic as a result of surgery or inflammation
• Over grown bacteria competes with the B12

A

Diphyllobothrium latum

Blind Loops

59
Q

SCREENING TEST (3)

A

• COMPLETE BLOOD COUNT &
RETICULOCYTE COUNT

• WHITE BLOOD CELL MANUAL
DIFFERENTIATION COUNT

• BILIRUBIN AND LACTATE
DEHYDROGENASE LEVELS

60
Q

• SPECIFIC DIAGNOSTIC TEST
•

A

Bone marrow examination

HEMA 1: LEC (23 decks)

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