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MLSCI 230 > Thalassemia > Flashcards

Thalassemia Flashcards

1
Q

alpha gene cluster

A

chromosome 16

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2
Q

beta gene cluster

A

chromosome 11

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3
Q

disorder of globin chain synthesis (quantitative)

A

thalassemia

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4
Q

T or F. we need correct proportions of each globin chain in order to have normal levels of each type of hemoglobin

A

T, pathologic effects arise from imbalance of globin-chain synthesis

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5
Q

most common monogenic diseases in humans

A

thalassemia

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6
Q

this classically follows malaria distribution

A

thalassemia

- selective pressure due to protection of heterozygotes from malaria

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7
Q

beta thalassemia

A
  • one beta gene on each copy of chrom 11
  • autosomal recessive inheritance
  • deletional/non-deletional
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8
Q

beta zero

A

mutations resulting in no beta chain production

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9
Q

beta +

A

mutations resulting in partial deficiency of beta chains

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10
Q

beta silent

A

very mild deficiency; little to no clinical impact

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11
Q

B/B+ or B/Bsilent

A

b-thal silent carrier

=> no hematologic or clinical abnormalities

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12
Q

B/B0

A

b-thal minor/trait

  • microcytosis, mild hemolytic anemia
  • no clinical symptoms
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13
Q

B0/B+ or B+/B+

A

b-thal intermedia

  • microcytosis, mild to moderate hemolytic anemia
  • moderate clinical symptoms; may require occasional transfusions but not dependent
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14
Q

B0/B0

A
  • homozygotes or compound heterozygotes; little to no beta globin production
  • severe microcytosis and hemolytic anemia
  • severe, transfusion dependent
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15
Q

Beta thal major

A
  • B0/B0
  • homozygous for non-functional B globin muttons
  • no production of HbA
  • increased HbA2, often increased HbF due to slight upreg of delta and gamma chains but usually insufficient to fully compensate
  • severe anemia starting ~ 6 mos of age (transfusion dependent)
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16
Q

Untreated B thal major lab features

A
  • Hgb below 70 g/L
  • MCV = 50-70 fL
  • MCH = 12-20 pg
  • marked microcytosis and hypochromia
  • marked poikilocytosis
  • RBC inclusions
  • polychromasia - nucleated RBCs
17
Q

iron precipitates

A

Pappenheimer bodies

18
Q

B thal poikilocytosis and RBC inclusions

A

poikilocytosis: target cells, tear drops, elliptocytes
inclusions: Basophilic stippling, Howell-Jolly bodies, Pappenheimer bodies

19
Q

B thal minor/trait

A
  • B/B0
  • generally asymptomatic, mild hematologic changes
    => may have mild symptoms of anemia
    => maybe have exacerbations of anemia during pregnancy
  • often identified incidentally
    => family studies, routine CBC
20
Q

B thal minor/trait lab features

A
  • elevated HbA2, increased HbF usually
  • Hgb = 90-110 g/L (normal); out of proportion w degree of microcytosis
  • MCV = 50-70 fL
  • MCH = 20-22 pg
  • RBC count elevated
21
Q

Blood film for B thal minor/trait

A
  • mild to moderate microcytosis and hypochromia
  • moderate poikilocytosis: target cells, few elliptocytes
  • RBC inclusions: sometimes basophilic stippling
22
Q

two alpha globin chains on each copy of this chromosome

A

16 (4 genes total)

23
Q

alpha chain mutations

A
  • reduced or absent alpha chain production from chromosome

- deletional, non-deletional (pt mutations, indels, splice sites, mRNA processing, etc.)

24
Q

alpha^0

A

deletion involving both alpha-globin genes on a chromosome

  • no alpha chain production from a chromosome
  • (–) haplotype
  • HS-40 deletion
25
Q

HS-40 deletion

A

(alpha^0)

important regulatory sequence 40kb upstream of zeta locus, required for alpha chain expression

26
Q

alpha^+

A

deletions or mutations affecting only one of the alpha genes on a chromosome

  • reduced alpha-globin production from that chromosome
  • (- alpha OR alpha -) haplotype; deletional
  • (alpha T alpha OR alpha alpha T) haplotype; non-deletional
27
Q

alpha thalassemia clinical syndromes depends on…

A

how many of the four genes are affected

28
Q

alpha thal silent carrier

A
  • (-a/aa) or aT/aa)
  • asymptomatic, little to no hematologic abnormalities
  • slight microcytosis?
29
Q

alpha thal minor/trait

A
  • (–/aa) or (-a/-a)
  • usually asymptomatic, mild hematologic abnormalities
  • microcytic anemia
30
Q

alpha thal intermedia

A
  • Hb H disease
  • (–/-a)
  • severe microcytic anemia
31
Q

Hb Bart’s hydrops fetalis syndrome

A
  • alpha thal major
  • (–/–)
  • severe, incompatible w life
32
Q

survival with Hb Bart’s

A

requires intrauterine transfusions and lifetime transfusion dependence

33
Q

this syndrome is a high risk of maternal complications at delivery due to very large placenta

A

Hb Bart’s (a thal major)

34
Q

loss of all 3 alpha genes or homozygous for severe non-deletion

A

Hb H disease

–/-a) or (aTa/aTa

35
Q

Mentzer index

A
  • MCV/RBC
  • <13 = thal trait likely
  • > 13 = thal less likely

MLSCI 230 (36 decks)

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