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Clinical Chemistry Lecture 3 > Hemoglobinopathies and Porphyrins > Flashcards

Hemoglobinopathies and Porphyrins Flashcards

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0
Q

Components of hemoglobin

A

1 Protein
2 Globin (2 pairs of polypeptide chains)
3 4 heme molecules

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1
Q

Oxygen carrying pigment of blood

A

Hemoglobin

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2
Q

Polypeptide

A

Binds one heme molecule

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3
Q

Heme

A

Consists of protoporphyrin IXa linked to an iron II ion to which oxygen becomes reversibly bound during oxygen transport

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4
Q

Hemoglobin F

A

Alpha, gamma

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5
Q

Hemoglobin A

A

Alpha, beta

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6
Q

Hemoglobin A2

A

Alpha, delta

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7
Q

Hemoglobin H

A

Beta

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8
Q

Hemoglobin Bart’s

A

Gamma

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9
Q

Hemoglobinopathies

A

Genetically determined abnormalities of protein synthesis

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10
Q

Qualitative hemoglobinopathies

A

Involve amino acid substitutions

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11
Q

Quantitative hemoglobinopathies

A

Involve defects in rate of synthesis

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12
Q

Effects of qualitative hemoglobinopathies

A

1 Clinically silent
2 Hemoglobin solubility
3 Hemoglobin stability
4 Oxygen carrying capacity

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13
Q

Symptoms of amino acid substitution

A

1 Pallor
2 Hypoxia
3 Cyanosis
4 Dizziness

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14
Q

Abnormal derivatives of hemoglobin

A

1 Methemoglobin
2 Sulfhemoglobin
3 Carboxyhemoglobin

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15
Q

Thalassemias

A

Inherited defects in the rate of synthesis of one of the globin chains

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16
Q

Consequences of thalassemia

A

1 Ineffective erythropoiesis
2 Hemolysis
3 Anemia

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17
Q

Congenital methemoglobinemia

A

Cyanosis

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18
Q

Sulfhemoglobin

A

1 Poorly characterized derivatives of hemoglobin

2 Incapable of carrying oxygen

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19
Q

Oxidized hemoglobin with iron in the ferric form

A

Methemoglobin

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20
Q

Result to methemoglobin

A

1 Normally produced in RBCs
2 Inherited deficiency of reductase enzyme
3 Ingestion of large amounts of drugs (e.g. Sulfonamides)

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21
Q

Brown color to plasma

A

Methemalbumin

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22
Q

Brown color to urine

A

Free methemoglobin

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23
Q

Results of toxic methemoglobinemia

A

1 Anemia
2 Vascular collapse
3 Death

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24
Q

The affinity of hemoglobin for this gas is approximately 200x greater than for oxygen

A

Carbon monoxide

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25
Q

Carboxyhemoglobin

A

Formed from hemoglobin in the presence of carbon monoxide

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26
Q

T or F. Only a small amount of carbon monoxide is needed to reduce oxygen carrying capacity of blood

A

T

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27
Q

Effect of carboxyhemoglobin in oxyhemoglobin dissociation curve

A

Left shift decreasing availability of oxygen to tissues

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28
Q

Oxyhemoglobin dissociation curve

A 
1 Left shift
Increased affinity
Decreased temperature
Decreased 2-3 DPG
Decreased [H+]
CO
2 Right shift
Reduced affinity
Increased temperature
Increased 2-3 DPG
Increased [H+]
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29
Q

Porphyrias

A 
1 Gamma-Aminolevulinic acid dehydratase porphyria
2 Acute intermittent porphyria
3 Congenital erythropoietic porphyria
4 Porphyria cutanea tarda
5 Hereditary coproporphyria
6 Variegate porphyria
7 Erythropoietic protoporphyria
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30
Q

Reduce heme molecule

A

Porphyrins

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31
Q

Causes accumulation of ALA synthase

A

Deficiency in one of the enzymes

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32
Q

Major sites of porphyrin synthesis

A

1 Liver

2 Erythroid bone marrow

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33
Q

Characteristics of porphyrins

A

1 Dark red in color

2 Intensely fluorescent

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34
Q

Porphyrins

A

Product of excreted porphyrinogens (oxidized)that are unstable in the feces or urine

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35
Q

Results in formation of excessive quantities of porphyrin precursors or porphyrins

A

Partial deficiency of one of the enzymes of porphyrin synthesis leading to decreased formation of heme –> ALA synthase from inhibition

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36
Q

Autosomal dominant disease that results from defects in the enzyme porphobilinogen deaminase

A

Acute intermittent porphyria

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37
Q

Predominant problem of acute intermittent porphyria

A

Neurologic damage (that leads to peripheral and autonomic neuropathies and psychiatric manifestations)

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38
Q

Inducers of porphyria

A

Chemicals or situations that boost heme synthesis (i.e. Fasting and medications)

39
Q

Sequence of events in attacks caused by acute intermittent porphyria

A

1 Abdominal pain
2 Psychiatric symptoms such as hysteria
3 Peripheral neuropathies, mainly motor neuropathies

40
Q

Associated with porphyria

A

Drugs that lead to increased activity of the hepatic P450 system (i.e. Phenobarbital, sulfonamides, estrogens, alcohol)

41
Q

Biologically useless but cause cutaneous photosensitivity characterized by blisters, erosions, and scarring of light exposed skin

A

Porphyrins of the isomer I type

42
Q

Congenital erythropoietic porphyria

A

Inheritance of 2 mutant alleles for the gene encoding the enzyme uroporphyrinogen III synthase leading to accumulation of porphyrins of the isomer I type

43
Q

Causes mutilation

A

Chronic damage of skin, cartilage, and bones

44
Q

Signs and symptoms of congenital erythropoietic porphyria

A 
1 Hypertrichosis
2 Erythrodontia
3 Reddish-colored urine
4 Hemolytic anemia
5 Splenomegaly
6 Osseos fragility
45
Q

Porphyria cutanea tarda

A

Group of acquired and familial disorders in which activity of the heme synthetic enzyme uroporphyrinogen decarboxylase (UROD) is deficient

46
Q

Cause of manifestations of porphyria cutanea tarda

A

Increased mechanical fragility after sunlight exposure

47
Q

Erosions and blisters form painful indolent sores that heal with milia, dyspigmentation, and scarring

A

Porphyria cutanea tarda

48
Q

Contributory factors of porphyria cutanea tarda

A 
1 Ethanol intake
2 Estrogen therapies
3 Hemochromatosis genes
4 Hepatitis
5 Human immunodeficiency viral infections
49
Q

Requirement of clinical expression of both sporadic and familial porphyria cutanea tarda

A

1 Exposure to environmental or infectious agents

2 Presence of existing conditions that adversely affect hepatocytes

50
Q

Other common features of porphyria cutanea tarda

A

1 Hypertrichosis
2 Sclerodermalike plaques that may develop dystrophic calcification
3 Excretion of discolored urine caused by porphyrin pigments

51
Q

Porphyria that causes urine that resembles port wine or tea

A

Porphyria cutanea tarda

52
Q

Total iron content of the adult body

A

Approximately 4 g (2/3 in hemoglobin)

53
Q

Contain 1/4 of the body’s iron

A

Iron stores (spleen, liver, bone marrow)

54
Q

T or F. Most of the remainder of iron is in myoglobin and other hemoproteins

A

T

55
Q

0.1% iron

A

In plasma where it is bound to transferrin

56
Q

Main site of iron absorption

A

Small bowel

57
Q

Readily absorbed iron

A

Ferrous iron

58
Q

Dietary iron

A

Ferric iron

59
Q

Important in iron absorption

A

Gastric secretions

60
Q

Mean daily intake of iron

A

About 20 mg but less than 10% is absorbed

61
Q

Facilitate iron absorption

A

1 Ascorbic acid

2 Reducing substances

62
Q

Decrease absorption of iron

A

1 Phytic acid
2 Phosphates
3 Oxalates

63
Q

Iron absorption and transport

A

1 Iron is absorbed in intestinal mucosal cells
2 Iron is transported directly into the bloodstream or combines with apoferritin to form ferritin
3 In the blood, iron is transported mainly bound to transferrin. Transferrin is normally 1/3 saturated with iron
4 Iron is lost from the body in feces, desquamation of skin, and menstrual blood loss

64
Q

No physiologic excretion mechanism

A

Iron

65
Q

Transferrin: 75% of iron

A

Hemoglobin/erythropoiesis

66
Q

Transferrin: 10-20% of iron

A

Ferritin (stores iron in liver and heart)

67
Q

Transferrin: 5-15% of iron

A

Other processes

68
Q

Diagnostic tests for iron status

A

1 Plasma iron
2 Plasma total iron binding capacity
3 Plasma ferritin

69
Q

Associated with low plasma concentrations

A

1 Infection
2 Trauma
3 Chronic inflammatory disorders
4 Neoplasia

70
Q

Late feature of iron deficiency

A

Decreased levels of plasma iron

71
Q

Plasma iron

A

Useful in diagnosis of hemochromatosis

72
Q

Functional measurement of transferrin concentration

A

Plasma total iron binding capacity

73
Q

Normal value of transferrin saturation

A

33%

74
Q

Transferrin saturation

A

Transferrin saturation = iron/TIBC x 100

75
Q

Increases TIBC

A

Iron deficiency

76
Q

Decreases transferrin saturation

A

1 Iron deficiency
2 Pregnancy
3 Chronic disease

77
Q

Consistently increased in iron overload

A

Transferrin saturation

78
Q

Normal range of plasma ferritin

A

20-300 mcg/L

79
Q

Plasma ferritin

A

1 Low: decrease in body iron stores
2 Normal value: acutely ill (acute phase protein and patients with iron deficiency)
3 Increased: hemochromatosis, liver disease, cancer

80
Q

PBG deaminase

A

Acute intermittent porphyria

81
Q

Coproporphyrinogen

A

Hereditary coproporphyria

82
Q

Uroporphyrinogen I synthase

A

Congenital erythropoietic porphyria

83
Q

UPG III synthase

A

Congenital erythropoietic porphyria

84
Q

Protoporphyrinogen oxidase

A

Variegate porphyria

85
Q

Uroporphyrinogen decarboxylase

A

Porphyria cutanea tarda

86
Q

Clinical features of acute intermittent porphyria

A

Abdominal pain

Psychiatric symptoms

87
Q

Clinical features of congenital erythropoietic porphyria

A

1 Photosensitivity
2 Red urine, teeth
3 Hemolysis

88
Q

Clinical features of hereditary coproporphyria

A

Photosensitivity

89
Q

Clinical features of variegate porphyria

A

Photosensitivity

90
Q

Clinical features of porphyria cutanea tarda

A

Photosensitivity

91
Q

Exacerbating factors of acute intermittent porphyria

A

Steroid hormones

92
Q

Exacerbating factors of congenital erythropoietic porphyria

A

Sunlight

93
Q

Exacerbating factors of hereditary coproporphyria

A

Stress

94
Q

Exacerbating factors of variegate porphyria

A

Stress

95
Q

Exacerbating factors of porphyria cutanea tarda

A

1 Alcohol
2 Hepatic injury
3 Iron overload

Clinical Chemistry Lecture 3 (9 decks)

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