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Evolution and natural selection
Independent assortment of genes and linkage
Mendelian genetics and punnett squares
Alagille syndrome (NORD)
Familial adenomatous polyposis
Multiple endocrine neoplasia
Polycystic kidney disease
Treacher Collins syndrome
von Hippel-Lindau disease
Gaucher disease (NORD)
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Niemann-Pick disease type C
Niemann-Pick disease types A and B (NORD)
Primary ciliary dyskinesia
Sickle cell disease (NORD)
Tay-Sachs disease (NORD)
Cri du chat syndrome
Fragile X syndrome
Down syndrome (Trisomy 21)
Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Ornithine transcarbamylase deficiency
Autosomal trisomies: Pathology review
Miscellaneous genetic disorders: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
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Sickle Cell Anemia: A Patient's Journey
Sickle Cell Anemia (Management)
Sickle Cell Anemia (Mechanism)
Sickle Cell Anemia (Signs and Complications)
Sickle Cell Disease
sickle cell anemia p. 415
in sickle cell anemia p. 421
sickle cell anemia in p. 415
in anemia taxonomy p. 423
ESR in p. 210
sickle cells in p. 421
autosplenectomy p. 735
missense mutation p. 38
osteonecrosis and p. 468
postsplenectomy state in p. 96
priapism p. 671
renal papillary necrosis p. 623
sickle cell disease p. 38
Sickle cell disease, also called sickle cell anemia or just “sickle cell,” is a genetic disease where red blood cells can take the shape of a crescent, or sickle, and that change allows them to more easily be destroyed, causing anemia among other things.
Sickle cell disease is caused by defective hemoglobin, which is the oxygen-carrying protein in red blood cells. Hemoglobin is actually made up of four peptide chains, each bound to a heme group.
Different hemoglobins have different combinations of these chains. Hemoglobin A (or HbA), made up of two α-globin and two β-globin peptide chains, is the primary hemoglobin affected in sickle cell.
Specifically, the β-globin chains end up misshapen. This is because of a mutation in the beta globin gene, or HBB gene.
Sickle cell is an autosomal recessive disease, so a mutation in both copies of the beta globin gene is needed to get the disease; if the person has just one copy of the mutation and one normal HBB gene, then they’re a sickle cell carrier, also called sickle trait.
Having sickle trait doesn’t cause health problems unless the person is exposed to extreme conditions like high altitude or dehydration, where some sickle cell disease-like symptoms can crop up.
What it does do is decrease the severity of infection by Plasmodium falciparum malaria, so in parts of the world with a high malaria burden, like Africa and pockets of southern Asia, those with sickle trait actually have an evolutionary advantage.
This phenomenon is called heterozygote advantage, and it's unfortunate consequence is a high rate of sickle cell disease in people from these parts of the world.
Almost always, the sickle cell mutation is a nonconservative missense mutation that results in the 6th amino acid of beta globin being a valine instead of glutamic acid.
Sickle cell disease is an autosomal recessive genetic disorder, in which the beta-globin subunit of hemoglobin is misshapen, causing red blood cells to sickle when deoxygenated, which leads to their premature destruction as well as vaso-occlusion. Sickle-cell disease is associated with several acute and chronic health problems, such as severe infections, attacks of severe pain ("sickle-cell crisis"), stroke, and an increased risk of death.
Symptoms of sickle cell disease can vary and may include episodes of severe pain, fatigue, shortness of breath, anemia, and frequent infections. The severity and frequency of symptoms can vary widely among individuals with the condition, and some people may experience only mild symptoms, while others may have more severe and frequent episodes of pain and organ damage.
Treatment for sickle cell disease may involve pain management, blood transfusions, and antibiotics to prevent infections. In some cases, a bone marrow transplant may be necessary to cure the condition. Additionally, individuals with sickle cell disease may need to make lifestyle changes, such as avoiding extreme temperatures, staying hydrated, and managing stress, to help prevent and manage symptoms.
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