Sickle cell disease (NORD)

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Sickle cell disease (NORD)

Information for patients and families

Information for patients and families

Information for patients and families

Information for patients and families


Sickle cell disease (NORD)


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USMLE® Step 1 questions

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High Yield Notes

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Sickle cell disease (NORD)

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USMLE® Step 1 style questions USMLE

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A 35-year-old man comes to the primary care office complaining of mild fatigue and shortness of breath. The patient has a past medical history significant for episodes of jaundice and intermittent right upper quadrant abdominal pain, which he has never been to the doctor for before. Temperature is 37.2°C (98.9°F), pulse is 72/min, respirations are 18/min, and blood pressure is 128/88 mmHg. Physical examination shows splenomegaly. Laboratory tests are obtained, and the results are shown below.  

Peripheral blood smear shows hexagonal crystals and target cells. This patient’s disease is most likely caused by a substitution of glutamic acid with which of the following amino acids?

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Aplastic crisis

sickle cell anemia p. 417


sickle cell anemia p. 417

Avascular necrosis p. 473

sickle cell anemia p. 417


sickle cell anemia p. 417


in sickle cell anemia p. 423

Hydroxyurea p. 448

sickle cell anemia p. 417


sickle cell anemia in p. 417

Osteomyelitis p. 177

sickle cell anemia p. 417

Priapism p. 675

sickle cell anemia p. 417

Renal papillary necrosis p. 625

sickle cell anemia p. 417

Sickle cell anemia p. 417

in anemia taxonomy p. 425

ESR in p. 212

sickle cells in p. 423

Sickle cell disease

autosplenectomy p. 730

missense mutation p. 38

osteonecrosis and p. 473

postsplenectomy state in p. 96

priapism p. 675

renal papillary necrosis p. 627

Stroke p. 529

sickle cell anemia p. 417


sickle cell disease p. 38


Content Reviewers

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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