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5 Red Blood Cell Disorders > 5.2-3 Microcytic anemia--Thalassemia > Flashcards

5.2-3 Microcytic anemia--Thalassemia Flashcards

1
Q

Alpha-thalassemia

-cis vs trans deletions: what populations?

A
  1. Cis: Asians. may explain the increased spontaneous abortion rate in Asia.
  2. Trans: Africans
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1
Q

Parvovirus B19:

in what anemia is this high risk?

A

Beta-thalassemia major

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2
Q

Beta-thalassemia major

-tx, complications of tx

A
  • chronic transfusions
  • risk for secondary hemochromotosis
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3
Q

What is HbH?

Hb Barts?

A

HbH: beta chain tetramers, in alpha thalassemia with 3 alpha genes deleted

Hb Barts: gamma chain tetramers, in alpha thalassemia with 4 genes deleted. (death in utero)

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3
Q

Infant with severe anemia a few months after birth:

suspect what

A

Beta-thalassemia major

(symptoms start after loss of HbF a few months after birth)

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4
Q

Beta-thalassemia minor

-what is the key lab finding for this?

A

-Increased HbA2 in Hb electrophoresis (5%, normal 2.5%)

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6
Q

Thalassemia

  • mech of anemia
  • what size RBCs
A

-low production of globin chains means low Hb

(Hb = heme + globin)

-Low Hb means microcytic, hypochromic RBCs

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6
Q

Beta-thalassemia major

-how do unpaired alpha chains cause anemia?

A
  • unpaired alpha chains precipitate and damage RBC membrane, resulting in:
    1. ineffective erythropoeisis
    2. increased RBC destruction in spleen
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8
Q

Thalassemia

-what specific malaria are carriers protected from?

A

Plasmodium falciparum

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8
Q

What are the normal types of Hb in the body?

A
  1. HbF–A2Y2
  2. HbA–A2B2
  3. HbA2–A2D2
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9
Q

Alpha-thalassemia

-2 genes deleted. symptoms?

A

Mild anemia with increased RBC count (RBCs have low Hb!)

  1. Cis deletion:

increased risk of severe thalassemia in offspring (b/c offspring now only need one bad chromosome from the other parent if they inherit the cis deletion)

  1. Trans deletion.
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10
Q

Alpha and Beta globin genes

  1. how many alleles
  2. on which chromosome?
A
  1. Alpha: 4 alleles, chromosome 16
  2. Beta: 2 alleles, chromosome 11
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10
Q

Beta-thalassemia minor

  • what gene mutations
  • symptoms
  • what you see on blood smear
A
  1. B/B0 (least severe)
  2. usu asymptomatic
  3. microcytic, hypochromic RBCs and target cells. Increased RBC count.
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11
Q

Beta-thalassemia major

  • genetic mutations
  • timeframe of symptoms
A
  1. B0/B0 (most severe combo)
  2. severe anemia several months after birth (after losing protection from HbF–A2Y2)
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13
Q

Beta-thalassemia

-what population

A

African and Mediterranean

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14
Q

Alpha-thalassemia

  • 3 alpha genes deleted. symptoms?
  • mech-
A
  • severe anemia.
  • Lack of alpha globins means beta chains form tetramers (HbH – B4) that damage RBCs

(HbH seen on electrophoresis)

16
Q

Thalassemia

-divided in what main categories

A

Alpha, Beta

17
Q

Target cell

-mech

A
  • RBC with low Hb–can form blebs in the center.
  • seen in Beta-thalassemia, Sickle cell anemia
18
Q

Beta-thalassemia minor:

-values in Hb electrophoresis

A

HbA: slightly decreased

HbA2: increased (5%, normal 2.5%)–key finding in beta-thalassemia minor

HbF: increased (2%, normal 1%)

19
Q

Pt with ‘crewcut skull’ on xray and ‘chipmunk facies’

-what’s happening, and what can the pt have?

A

Massive bone marrow erythroid hyperplasia

  • Beta-thalassemia major
  • Sickle Cell Anemia
21
Q

Beta-thalassemia major

-what do you see on blood smear

A

microcytic, hypochromic RBCs, with target cells and nucleated RBCs (released from spleen and liver hematopoeisis)

22
Q

Beta-thalassemia major

-values in Hb electrophoresis

A

HbA2 and HbF, but little or no HbA

23
Q

Beta-thalassemia major

-symptoms (3)

A
  1. severe anemia
  2. ‘crewcut skull’ and ‘chipmunk face’ from bone marrow expansion (very high EPO) into skull and facial bones.
  3. hepatosplenomegaly (extramedullary hematopoeisis)
24
Q

Beta-thalassemia major

-risk of emergency from what specific infection? why?

A

Parvovirus B19, can cause aplastic crisis

  • it infects erythroid precursors, so is dangerous in pts that are desperate for every RBC
  • in healthy ppl, the infection is usu self limiting and not severe, lasts a week.
25
Q

Beta-thalassemia

-What forms of mutated beta chains are there?

A

beta: normal production
beta0: decreased production of beta chain

beta+: no production of beta chain

26
Q

Alpha-thalassemia

-one gene deleted. symptoms?

A

asymptomatic

27
Q

Alpha-thalassemia

  • 4 alpha genes deleted. symptoms?
  • mech
A
  • lethal in utero (Hydrops fetalis)
  • Gamma chains (that would form HbF with alpha chains) form tetramers (Hb Barts), which damage RBCs.
  • Hb Barts detected on electrophoresis

5 Red Blood Cell Disorders (8 decks)

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