Haemoglobin Disorders II Flashcards
Sickle Cell disease
Sickle cell disease is a group of haemoglobin disorders in which the __________ is _________
sickle β-globin gene is inherited.
Sickle Cell disease
The sickle β-globin abnormality is caused by substitution of ______ for _________ in position ____ in the β globin-chain.
glutamic acid; valine
6
Sickle Cell disease
__________________ is the most common while the _______________________ also cause sickling disease.
Homozygous sickle cell anaemia (HbSS)
doubly heterozygote conditions of HbSC and Hb Sβthal
Homozygous Disease: Hb SS; Sickle cell anaemia.
The inheritance of 2 HbS gene one each from both parent.
T/F
T
Homozygous Disease: Hb SS; Sickle cell anaemia.
The disease was first described in 1904 by a Chicago based physcian, Dr. James Herrick who reported “ _______ and ______ shaped” red blood cells in a young man of _______ origin.
The patient had come to Dr. Herrick with complaints of shortness of breath, heart palpitations, abdominal pain, and _________ in his muscles.
He also felt _______ all the time, had _______, experienced attacks of ______, and had _____ on his legs. After noting these symptoms, the doctor took samples of his blood
peculiar elongated and sickle
Negroid
aches and pains; tired; headaches
dizziness; ulcers
Genetic basis of Sickle cell anaemia (HbSS)
•__________ mutation on the _____gene at _____ nucleotide, ____ Codon, aa in position _____, resulting in ______ instead of ________
• For comparison, Hb C a mutation at the same spot, leads to _____ instead of ———-
Single point
β
17th; 6th; 6
valine; glutamine
lysine; glutamine
Haemoglobin S production arises from _______________________ gene
Differ from HbA by ___________
an altered (mutated) “S” gene.
one amino acid substitution.
Pathogenesis
The substitution of a valine for a glutamine results in decreased _______ of (oxy or deoxy?) -HbS compared to (oxy or deoxy?) -HbA.
solubility ; deoxy
Deoxy
Pathogenesis
When _____genated, HbS tetramers form ———- which associate into _____ that ——————
deoxy
polymers
bundles
precipitate in the red cell
As long as HbS is in the oxygenated state it is (subtle or insoluble?)
solube
As long as HbS is in the _____genated state it is solube
oxy
Upon de-oxygenated, Hb becomes _______ and _______, _____ are formed which leads to _____.
Blood becomes more ________
insoluble and polymerise
tactoids
sickling
viscous
Consequences of polymerization of haemoglobin
Sickling of red cells
Loss of red blood cell ————-
__________ of red blood cells
________ of small vessels
_______damage
deformability
Haemolysis
Vaso-occlusion
End organ
Pathophysiologic effects of sickled cells.
Red cells carrying Hb S constantly ___________ on the arterial side to ________ on the venous side. Eventually, some cells become __________
switch from normal shape
sickled shape
irreversibly deformed,
Pathophysiologic effects of sickled cells.
Eventually, some cells become irreversibly deformed, resulting in:
1. ___________
2. ________ of ___________
Extra-vascular haemolysis
Compromise of micro circulation
Pathophysiologic effects of sickled cells.
- Extra-vascular haemolysis.
Conscientious function of the _____ to remove damaged or deformed cells targets the cells that ___________________________. The cells are trapped and removed by _________.
spleen
cannot traverse the narrow openings of the splenic sinusoids
macrophages
Pathophysiologic effects of sickled cells.
- Extra-vascular haemolysis.
◦ The deformed cells compromise the _______ of the spleen causing __________ and eventual _________
◦ Replacement of cells carrying HbS with the same abnormal cells causes ______ because of continuous _______ of the cells by the spleen and, later, by the ———-.
blood supply
repeated small infarctions
loss of splenic function.
anaemia; early destruction ; RES
Pathophysiologic effects of sickled cells.
Compromise of Microcirculation.
As red cells carrying HbS become ______ and lose their ability to ________. They create a ______ that ________.
sickled
traverse narrow passages; blockage
obstructs blood flow into the tissue
Pathophysiologic effects of sickled cells.
Compromise of Microcirculation.
The local anoxia that results from the blockage increase ____________and further aggravates the ________ and ___________ of abnormal haemoglobin.
oxygen extraction from the trapped red cells
deoxygenation and polymerization
Pathophysiologic effects of sickled cells.
Compromise of Microcirculation.
The compensatory action of the adjacent vessels releases more oxygen from the cells. This _____eases sickling and causes ————; of the situation.
incr
exacerbation
Pathophysiologic effects of sickled cells.
Compromise of Microcirculation.
Tissue damage from lack of oxygen is the cause of the ________ and _______ characteristic of sickle cell crises.
Vaso-occlusion promotes ___________________ injury
acute and chronic pain
ischemia-reperfusion (I-R)
Impaired rheology of the blood and aggregation of sickle erythrocytes with neutrophils, platelets, and endothelial cells causes stasis of blood flow and is referred to as _________
vaso-occlusion.
Factors promoting sickling
extreme heat/cold; cold
Dehydration
Acidosis
Factors promoting sickling
Hypoxemia: _______,________ ,______ , stasis of the circulation, , _______
altitude, operations, obstetric delivery,
violent exercise
Factors opposing sickling
The presence of non sickling haemoglobin:
Hb_____
Hb ______
F
A
Sickle-cell conditions are inherited from parents in much the same way as blood type, hair color and texture, eye color, and other physical traits.
T/F
T
The types of haemoglobin a person makes in the red blood cells depend on what hemoglobin genes are inherited from his parents
T/F
T
Inheritance
Sickle cell anemia is inherited in
an (Xlinked or autosomal?). (Dominant or recessive?) pattern, which means that __________ of the gene in each cell have mutations .
autosomal recessive
both copies
The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
T/F
T
If one parent has sickle-cell anaemia (SS) and the other has sickle-cell trait (AS), there is a ____% chance of a child’s having sickle-cell disease (SS) and a ____% chance of a child’s having sickle-cell trait (AS).
50; 50
When both parents have sickle-cell trait (AS), a child has a ____% chance of sickle-cell anaemia (SS)
25
Clinical features of SS
Clinical features are of _________ punctuated by _______.
severe haemolytic anaemia
crises
Clinical features of SS
The symptoms of anaemia are often mild in relation to the severity of the anaemia because ________________________
HbS gives up oxygen (O2) to tissues relatively easily compared with HbA, its O2 dissociation curve being shifted to the right.
Clinical features of SS
The clinical expression of Hb SS is very variable, some patients having an almost normal life, free of crises but others develop severe crises even as infants and may die in early childhood or as young adults.
T/F
T
Sickle cell Anaemia: Consequences of Haemolysis
__________
_________
____________
——————-
Anaemia
Jaundice
Gallstones
Vasculopathies
Sickle cell Crises may be:
______ or _______
vaso-occlusive
Anaemic
Sickle cell Crises may be:
vaso-occlusive: eg ______
Pain
Sickle cell Crises may be:
Anaemic: _____,_____,_____,______
Sequestration, Aplastic, Hyperhaemolytic Megaloblastic.
Vaso-occlusive (Pain) crises
These are the most frequent and are precipitated by such factors as ———-,———,———,——— (e.g. altitude, operations, obstetric delivery, stasis of the circulation, exposure to cold, violent exercise).
Infarcts can occur in a variety of organs including the _______(____,____,____ are commonly affected), the ——— and the _________
infection, acidosis, dehydration or de-oxygenation
bones
hips, shoulders and vertebrae
the lungs and the spleen.
Vaso-occlusive (Pain) crises
The most serious vaso-occlusion is of the _____ ( _________ occurs in 7% of all patients) or _________.
brain
Ischemic stroke
spinal cord