5.2-3 Microcytic anemia--Thalassemia Flashcards
Alpha-thalassemia
-cis vs trans deletions: what populations?
- Cis: Asians. may explain the increased spontaneous abortion rate in Asia.
- Trans: Africans
Parvovirus B19:
in what anemia is this high risk?
Beta-thalassemia major
Beta-thalassemia major
-tx, complications of tx
- chronic transfusions
- risk for secondary hemochromotosis
What is HbH?
Hb Barts?
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)
Infant with severe anemia a few months after birth:
suspect what
Beta-thalassemia major
(symptoms start after loss of HbF a few months after birth)
Beta-thalassemia minor
-what is the key lab finding for this?
-Increased HbA2 in Hb electrophoresis (5%, normal 2.5%)
Thalassemia
- mech of anemia
- what size RBCs
-low production of globin chains means low Hb
(Hb = heme + globin)
-Low Hb means microcytic, hypochromic RBCs
Beta-thalassemia major
-how do unpaired alpha chains cause anemia?
- unpaired alpha chains precipitate and damage RBC membrane, resulting in:
1. ineffective erythropoeisis
2. increased RBC destruction in spleen
Thalassemia
-what specific malaria are carriers protected from?
Plasmodium falciparum
What are the normal types of Hb in the body?
- HbF–A2Y2
- HbA–A2B2
- HbA2–A2D2
Alpha-thalassemia
-2 genes deleted. symptoms?
Mild anemia with increased RBC count (RBCs have low Hb!)
- 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)
- Trans deletion.
Alpha and Beta globin genes
- how many alleles
- on which chromosome?
- Alpha: 4 alleles, chromosome 16
- Beta: 2 alleles, chromosome 11
Beta-thalassemia minor
- what gene mutations
- symptoms
- what you see on blood smear
- B/B0 (least severe)
- usu asymptomatic
- microcytic, hypochromic RBCs and target cells. Increased RBC count.
Beta-thalassemia major
- genetic mutations
- timeframe of symptoms
- B0/B0 (most severe combo)
- severe anemia several months after birth (after losing protection from HbF–A2Y2)
Beta-thalassemia
-what population
African and Mediterranean
Alpha-thalassemia
- 3 alpha genes deleted. symptoms?
- mech-
- severe anemia.
- Lack of alpha globins means beta chains form tetramers (HbH – B4) that damage RBCs
(HbH seen on electrophoresis)
Thalassemia
-divided in what main categories
Alpha, Beta
Target cell
-mech
- RBC with low Hb–can form blebs in the center.
- seen in Beta-thalassemia, Sickle cell anemia
Beta-thalassemia minor:
-values in Hb electrophoresis
HbA: slightly decreased
HbA2: increased (5%, normal 2.5%)–key finding in beta-thalassemia minor
HbF: increased (2%, normal 1%)
Pt with ‘crewcut skull’ on xray and ‘chipmunk facies’
-what’s happening, and what can the pt have?
Massive bone marrow erythroid hyperplasia
- Beta-thalassemia major
- Sickle Cell Anemia
Beta-thalassemia major
-what do you see on blood smear
microcytic, hypochromic RBCs, with target cells and nucleated RBCs (released from spleen and liver hematopoeisis)
Beta-thalassemia major
-values in Hb electrophoresis
HbA2 and HbF, but little or no HbA
Beta-thalassemia major
-symptoms (3)
- severe anemia
- ‘crewcut skull’ and ‘chipmunk face’ from bone marrow expansion (very high EPO) into skull and facial bones.
- hepatosplenomegaly (extramedullary hematopoeisis)
Beta-thalassemia major
-risk of emergency from what specific infection? why?
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.
Beta-thalassemia
-What forms of mutated beta chains are there?
beta: normal production
beta0: decreased production of beta chain
beta+: no production of beta chain
Alpha-thalassemia
-one gene deleted. symptoms?
asymptomatic
Alpha-thalassemia
- 4 alpha genes deleted. symptoms?
- mech
- 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
