Module 7 Part 1 - Hematology Flashcards
Sickle Cell Anemia (SCA)
a group of autosomal recessive disorders which manifests as an anemia with sickle or crescent shaped RBCs d/t presence of abnormal type of Hgb S
What sort of genetic inheritance pattern is SCA?
Autosomal Recessive
What is Hgb S associated with besides SCA?
Protection from cerebral malaria (common disease in Sub-Sahara Africa
What populations most frequently have SCA?
Frequency of the disease is high in Mediterranean and African Populations
30% of their populations have the trait (carrier or disease)
What is the rate for an African American carrying the SCA gene (Sickle Cell Trait) in the US? How many African American newborns have SCA?
1 in 12 (8%) carrier rate
1 in 500 have SCA
90000-100000 people with SCA exist in the US currently with 50-70% reaching ages 40-50 – so its not longer a death sentence
What is the only treatment with a chance to cure SCA?
Bone Marrow Transplant
What are some examples of Sickle Cell Disorders?
Sickle Cell Anemia
Sickle Cell Hgb C
Sickle Cell Beta Thalassemia Disease
Under what conditions does Hgb S Sickle?
- Vasodilation causing conditions: Low pH, high H+ concentration, Acid build up (acidosis)
- Low O2, High CO2
- Exercise
- Dehydration
- Infection (especially bacterial)
- Stress and Anxiety
- Fever
- Exposure to the cold and high altitudes
If a person has the SCA trait (is a carrier) how much of their Hgb will be Hgb S?
Heterozygous for the trait (Ss) = 40% is Hgb S
If a person has the SCA disease how much of their Hgb will be Hgb S?
Homozygous Recessive (ss) = 90% Hgb S and a greater chance for sickling
Can Hgb S return to its original shape?
Yes! with enough oxygenation it can
However, the more times it does this the less likely it is to return to shape on subsequent events
What kind of Hgb is high in newborns? What do we do if the newborn will have SCA?
Hgb F
Hgb F is all metabolized by 5-6 mo post-birth, so if they are homozygous recessive we give hydroxyurea to increase Hgb F production so it is not metabolized as quickly and delay the sickling further out
What will be the hereditary pattern for parents that are AA (no SCA trait) and SS (homozygous rec for the trait) be like for SCA?
100% chance of child being a carrier
0% chance of children having SCA or being non carriers
What will the hereditary pattern for parents that are AS and SS be like for SCA?
50% chance of child having SCA
50% chance of being a carrier for SCA trait
What will the hereditary pattern be like for SCA if both parents are Heterozygous recessive for SCA trait?
50% chance of having the trait/being a character for the kids
25% chance the kid will have SCA
25% chance the child is normal with no trait or disease
How does SCA incidence differ between gender?
It does not since it is not sex linked
Lifespan of a normal RBC
120 days
Lifespan of a sickle cell
15-20 days
What is the structure of an RBC with normal Hgb?
smooth surfaced, flexible, disk that can mold its shape to move through arterioles, capillaries, and venules
What is the structure of an RBC with Hgb S?
Rough textured, rigid, elongated crescent shaped RBC
RBCs with Hgb S can only ___ and __ a certain amount of times
sickle and desickle
The process of sickling is reversible at first, but cells become susceptible to …
permanent entrapment by the macrophage system of the spleen and liver (can lead to impaired filtering)
What does entrapment of sickle cells by the macrophage system cause?
Hemolytic Anemia (increased destruction of RBCs resulting in Hgb deficiency)
Manifestations of SCA
Slightly jaundiced from hemolysis (sclera yellow, urine dark)
Painful excruciating crises / intense pain caused by vascular occlusion during sickling episodes
Sickling occurs more so in certain areas
Hypoxia from systemic anemia
Serious bacterial infection d/t inadequate splenic filtering of microorganisms
Potential Splenomegaly