HEMOGLOBINOPATHIES Flashcards

1
Q

-refers to a disease state involving the hemoglobin molecule
- are the most common genetic diseases

A

HEMOGLOBINOPATHIES

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2
Q

all hemoglobinopathies result from a β€”β€”β€”β€”in one or more genes that affect hemoglobin synthesis

A

point mutation

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3
Q
  • the genes that are mutated can code or either the proteins that make up the hemoglobin molecule or the proteins involved in synthesizing or regulating synthesis of the globin chains,
A

HEMOGLOBINOPATHIES

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4
Q

affects hemoglobin synthesis in one of two ways:

A

qualitatively HMOGLOBINOPATHIES
quantitatively THALASSEMIA

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5
Q

Factors that may alter the manner in which globin chains fold:

A

a. Change in amino acid charge
b. Size of the substituted amino acid

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6
Q

Detection and Identification of Hemoglobinopathies

Purpose -Primary screening procedure
Specimen -Whole blood (EDTA/heparin)
pH Alkaline 8.4
Principle -At alkaline buffer, hemoglobin is negatively charged and will migrate towards the anode

A

Cellulose acetate electrophoresis

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7
Q

Purpose -Confirm variants of hemoglobin
Specimen -Whole blood (EDTA)
pH Acid 6.0-6.2
Principle: In an acid pH, some hemoglobins assume a negative charge and migrate toward the anode, while others are positively charged and migrate toward the cathode

A

Citrate agar electrophoresis

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8
Q
  • are the most common form of hemoglobinopathy
  • are either homozygous for Hb S or are compound heterozygotes
  • Hb S polymers are long and thin
A

SICKLE CELL DISEASE

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9
Q

-Separate Hb type in cation exchange column and usually requires only one sample injection
- can identify and quantitate low levels of Hb A2 and HbF

A

HPLC

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10
Q

-Best used in diagnosis of thalassemia rather than hemoglobinopathies
- also commonly used to quantitate HbA1c

A

HPLC

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11
Q
  • defined by the structural formula Ξ±2B26Gluβ†’Val, which indicates that on the Ξ² chain at position 6, glutamic acid is replaced by valine
A

Hb SS

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12
Q

offer some protection against cerebral falciparum malaria

A

Hb SS

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13
Q

Sickle cells come in two forms:

A

a. Reversible sickle cells - change in shape in response to oxygen tension

b. Irreversible sickle cells - do not change their shape regardless of the change in oxygen tension or degree
of hemoglobin polymerization

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14
Q

Clinical Features:
Hallmark of SCD:

A

-Vasoocclusive crisis
- Acute chest syndrome
- Pulmonary hyprtension
- Increased susceptibility to S. aureus, S. pneumoniae, H. influenzae
- Aplastic episodes

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15
Q

Laboratory findings: SICKLE CELL DISEASE /Hb SS
Hallmark:

A

presence of sickle cells and target cells

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16
Q
  • refers to the heterozygous state (Hb AS)
  • generally asymptomatic and present with no clinical or hematologic manifestations
  • failure to concentrate urine is the only consistent abnormality found in patients with sickle cell disease
A

Sickle cell trait

17
Q

Sickle cell trait Laboratory findings:

A

Normal RBC morphology, with the exception of a few target cells

18
Q

Laboratory diagnosis: sickle cell

A

Sickling Test

Solubility Test

19
Q

sodium metabisulfite
Principle: addition of sodium metabisulfite enhances deoxygenation and sickling of the red blood cell

Specimen: Whole blood (EDTA/heparin)
Positive result: Sickling of cells

A

Sickling Test

20
Q

sodium dithionite
- most common screening test for Hb S

Principle: addition of sodium hydrosulfite (dithionite) results to immediate lysis of RBC due to saponin and
reduction of of iron to its ferric state.

Specimen: Whole blood (EDTA/heparin/sodium citrate) Positive result: Turbidity

A

Solubility Test

21
Q

defined by the structural formula α2B26Glu→Val, which indicates that on the β chain at position 6, glutamic acid is replaced by valine

A

Hb SS

22
Q
  • defined by the structural formula Ξ±2Ξ²2 6 Gluβ†’Lys, in which lysine is substituted for glutamic acid in position 6 of the Ξ² chain
A

HEMOGLOBIN C DISEASES

23
Q

-polymers form a short, thick crystal within the RBCs (does not alter RBC shape to the extent that Hb S does)
- VOC Vasoocclusive crisis does not occur
- yields a negative result on the hemoglobin solubility test

A

HEMOGLOBIN C DISEASES

24
Q

Double substitution on the Ξ² chain
(substitution of valine for glutamic acid at position 6 of the Ξ² chain, and the substitution at position 73 of aspartic acid for asparagine)

A

Hb C Harlem/Hb C Georgetown

25
Q

Double mutation in the same beta chain
🩸Beta 6 Glutamic to valine
🩸at position 73 of aspartic acid for asparagine

A

Hb C Harlem/Hb C Georgetown

26
Q

Lysine is substituted for glutamic acid in position 26
(Hb EE resembles thalassemia trait)

A

Hb E

27
Q

Substitution of lysine for glutamic acid at amino acid position 121

A

Hb O-Arab

28
Q

2 substitution of a tyrosine for either proximal or distal histidine

A

Hb M

29
Q

Double substitution glutamic to lysine and glutamic to valine

Not same beta mutation

A

Hb SC