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Simple notes on sickle cell anemia
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Genetic DisorderSickle Cell
What is Sickle cell Disease
Sickle Cell disease: is a genetic disorder that affects erythrocytes (RBC) causing them to become sickle or crescent shaped.
The effects of this condition due to an abnormality of the hemoglobin molecules found in erythrocytes.
Erythrocytes
Red Blood Cells
Erythropoesis
Contains Hemoglobin
Transports oxygen
100 – 120 days
No Nucleus
Squeeze through Capillaries
Smooth and round
Hemoglobin
The oxygen-carrying pigment and predominant protein in the red blood cells.
Hemoglobin forms an unstable, reversible bond with oxygen.
Oxyhemoglobin: Oxygenated ( bright red). Deoxyhemoglobin: Reduced ( purple-blue).
Hemoglobin
• Each hemoglobin molecule is made up of four heme groups surrounding a globin group.
• Heme contains iron and gives a red color to the molecule.
• Globin consists of two linked pairs of polypeptide chains.
Types of Hemoglobin
Normal
Hb A
Hb A2
Hb F
Abnormal (350)
Hb S
Hb C
Hb E
Sickle Cell DiseaseHemoglobin SS Disease
Hemoglobin SC Disease
Beta-Zero Thalassemia
Hemoglobin SB+ (Beta) Thalassemia
Sickle Cell Anemia
History
• The error in the hemoglobin gene results from a genetic mutation that occurred many thousands of years ago in people in parts of Africa, the Mediterranean basin, the Middle East, and India.
Sickle Cell Gene Severe Malaria
The origin of Sickle Cell anemia The change in cell structure arises from a change inthe structure of hemoglobin.
A single change in an amino acid causes hemoglobinto aggregate.
Sickle Cell Mutation
Hemoglobin A
Hemoglobin S
Genetic Recessive Disorder
Sickle Cell anemia is a recessive genetic disorder resulting from a mutation on chromosome 11, which is responsible for the synthesis of B – strand of the hemoglobin molecule.
It can be passed from generation to generation but is only majorly presented if the offspring has both allele for the disorder.
Inheritance of Sickle Cell Anemia
If one parent has sickle cell trait (HbAS) and the other does not carry the sickle hemoglobin at all (HbAA) then none of the children will have sickle cell anemia. There is a one in two (50%) chance that any given child will get one copy of the HbAS gene and therefore have the sickle cell trait. It is equally likely that any given child will get two HbAA genes and be completely unaffected.
Source from http://www.sicklecellsociety.org/education/inherit.htm#anchor298279
Inheritance of Sickle Cell Anemia
If both parents have sickle cell trait (HbAS) there is a one in four (25%) chance that any given child could be born with sickle cell anemia.
There is also a one in four chance that any given child could be completely unaffected.
There is a one in two (50%) chance that any given child will get the sickle cell trait.
Source from http://www.sicklecellsociety.org/education/inherit.htm#anchor298279
Inheritance of Sickle Cell Anemia
If one parent has sickle cell trait (HbAS) and the other has sickle cell anaemia (HbSS) there is a one in two (50%) chance that any given child will get sickle cell trait and a one in two (50%) chance that any given child will get sickle cell anemia.
No children will be completely unaffected.
Inheritance of Sickle Cell Anemia
If one parent has sickle cell anaemia (HbSS) and the other is completely unaffected (HbAA) then all the children will have sickle cell trait.
None will have sickle cell anemia.
The parent who has sickle cell anemia (HbSS) can only pass the sickle hemoglobin gene to each of their children.
Source from http://www.sicklecellsociety.org/education/inherit.htm#anchor298279
Sickle Cell Trait
Sickle hemoglobin (S) + Normal hemoglobin (A) in RBC
Adequate amount of normal Hb (A) in red blood cells RBC remain flexible Carrier
Do Not have the symptoms of the sickle cell disorders, with 2 exceptions:
Pain when Less Oxygen than usual Minute kidney problems
Mechanism• When sickle hemoglobin (HbS) gives up its oxygen
to the tissues, HbS sticks together – Forms long rods form inside RBC – RBC become rigid, inflexible, and sickle-shaped– Unable to squeeze through small blood vessels, instead
blocks small blood vessels– Less oxygen to tissues of body
• RBCs containing HbS have a shorter lifespan– Normally 20 days– Chronic state of anaemia
Signs and Symptoms of
Sickle Cell Anemia
Jaundice
Pain Episodes
AnemiaInfections
Ulcers on the Legs
Eye Problems
Complications associated with Sickle Cell anemia
• Sickle cells become sticky, rigid and elongated when they are not saturated with oxygen.
• They then stick together and hinders blood flow leading to a wide spectrum of complications.
Complications of Sickle Cell
Anemia
Hand-Foot Syndrome
Splenic Crisis
Acute Chest Syndrome
Pulmonary Hypertension
StrokePriapism
Gallstones
Blindness
Organ Damage
Treatments
Effective treatments are available to help relieve the symptoms and complications of sickle cell anemia, but in most cases there’s no cure.
Pain medicine: acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), and narcotics such as meperidine, morphine, oxycodone, and etc.
Heating padsHydroxyurea, Folic AcidBlood Transfusions
Screening1. Hemoglobin Electrophoresis
Simple Blood test Routine screening in high risk groups
• During pregnancy• Before anesthesia
2. Prenatal Testing Amniocentesis
16 and 18 weeks of the pregnancy small risk of causing a miscarriage (1 in 100)
Chorionic villus sampling (CVS) 9th or 10th week of pregnancy very small amount of material from the developing placenta slightly higher chance of miscarriage
The End