WBR0097: Difference between revisions
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|MainCategory=Genetics, Histology | |MainCategory=Genetics, Histology | ||
|SubCategory=Hematology | |SubCategory=Hematology | ||
|Prompt=A 3 week old newborn is brought into the pediatric emergency department by his mother for colic and the appearance of jaundice | |Prompt=A 3-week-old newborn is brought into the pediatric emergency department by his mother for colic and the appearance of jaundice for the past several days. On physical exam, the child’s spleen is readily palpable. Laboratory values reveal hyperbilirubinemia, and decreased RBC count. A blood smear from the child is shown below. Which of the following is the most likely cause of this child’s condition? | ||
{{#!:[[File:Hereditary Spherocytosis smear 2010-03-17.JPG|center|400px]] }} | {{#!:[[File:Hereditary Spherocytosis smear 2010-03-17.JPG|center|400px]] }} | ||
|Explanation=The patient in this vignette is most likely suffering from hereditary spherocytosis. Hereditary sphereocytosis is an autosomal dominant condition | |Explanation=The patient in this vignette is most likely suffering from hereditary spherocytosis. Hereditary sphereocytosis is an autosomal dominant condition that causes an auto-hemolytic anemia. It is characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped (donut-shaped), and therefore more prone to hemolysis. On blood smear, Howell-Jolly bodies may be seen within red blood cells. Signs and symptoms include anemia, jaundice, and an enlarged spleen (splenomegaly). Acute cases can cause hypoxia through anemia and acute kernicterus through hyperbilirubinemia, particularly in newborns. Most cases can be detected soon after birth. The number of immature red blood cells (reticulocyte count) will be elevated. Hereditary spherocytosis is caused by a variety of molecular defects in the genes that code for spectrin (alpha and beta), ankyrin, band 3 protein, protein 4.2, and other erythrocyte membrane proteins. Mutations in ankyrin are the most common. | ||
|AnswerA=Mutation of glutamic acid to valine in the beta globin gene | |||
|AnswerAExp=A missense mutation of the sixth amino acid of the beta-globin gene to valine causes [[sickle cell anemia]]. Beta-globin mutations are not associated with Hereditary spherocytosis. | |||
|AnswerA=Mutation of glutamic acid to valine in the Beta globin | |||
|AnswerB=Mutation of three copies of the alpha-globin gene | |AnswerB=Mutation of three copies of the alpha-globin gene | ||
|AnswerBExp=Mutation of three copies of the alpha-globin gene would cause the Hemoglin H disease variant of [[alpha thalassemia]]. | |||
|AnswerC=Mutation of ankyrin | |AnswerC=Mutation of ankyrin | ||
|AnswerCExp=Ankyrin mutations are the most common genetic lesion of hereditary spherocytosis. | |||
|AnswerD=Mutation of spectryin | |AnswerD=Mutation of spectryin | ||
|AnswerDExp=[[Spectrin]] deficiency is common to all forms of hereditary spherocytosis. However, spectrin deficiency is more often secondary to ankyrin mutations than to spectrin mutations. | |||
|AnswerE=Nonsense mutation in the beta-globin gene | |AnswerE=Nonsense mutation in the beta-globin gene | ||
|AnswerEExp=Nonsense mutations of the beta-globin gene cause [[beta-thalassemia]]. A missense mutation of the sixth amino acid of the beta-globin gene to valine causes [[sickle cell anemia]]. Beta-globin mutations are not associated with Hereditary spherocytosis. | |||
|EducationalObjectives=Hereditary spherocytosis is caused by mutations in the ankyrin and spectrin genes. Ankyrin mutations are the more common of the two. | |||
|References=First Aid 2014 page 386 ; First Aid 2012 page 384 | |||
|RightAnswer=C | |RightAnswer=C | ||
|WBRKeyword=Hematology, Genetics, Hereditary spherocytosis, Spherocytosis, RBC, | |||
|Approved=Yes | |Approved=Yes | ||
}} | }} |
Revision as of 21:48, 22 March 2014
Author | PageAuthor::William J Gibson |
---|---|
Exam Type | ExamType::USMLE Step 1 |
Main Category | MainCategory::Genetics, MainCategory::Histology |
Sub Category | SubCategory::Hematology |
Prompt | [[Prompt::A 3-week-old newborn is brought into the pediatric emergency department by his mother for colic and the appearance of jaundice for the past several days. On physical exam, the child’s spleen is readily palpable. Laboratory values reveal hyperbilirubinemia, and decreased RBC count. A blood smear from the child is shown below. Which of the following is the most likely cause of this child’s condition? {{#!: }}]] |
Answer A | AnswerA::Mutation of glutamic acid to valine in the beta globin gene |
Answer A Explanation | [[AnswerAExp::A missense mutation of the sixth amino acid of the beta-globin gene to valine causes sickle cell anemia. Beta-globin mutations are not associated with Hereditary spherocytosis.]] |
Answer B | AnswerB::Mutation of three copies of the alpha-globin gene |
Answer B Explanation | [[AnswerBExp::Mutation of three copies of the alpha-globin gene would cause the Hemoglin H disease variant of alpha thalassemia.]] |
Answer C | AnswerC::Mutation of ankyrin |
Answer C Explanation | AnswerCExp::Ankyrin mutations are the most common genetic lesion of hereditary spherocytosis. |
Answer D | AnswerD::Mutation of spectryin |
Answer D Explanation | [[AnswerDExp::Spectrin deficiency is common to all forms of hereditary spherocytosis. However, spectrin deficiency is more often secondary to ankyrin mutations than to spectrin mutations.]] |
Answer E | AnswerE::Nonsense mutation in the beta-globin gene |
Answer E Explanation | [[AnswerEExp::Nonsense mutations of the beta-globin gene cause beta-thalassemia. A missense mutation of the sixth amino acid of the beta-globin gene to valine causes sickle cell anemia. Beta-globin mutations are not associated with Hereditary spherocytosis.]] |
Right Answer | RightAnswer::C |
Explanation | [[Explanation::The patient in this vignette is most likely suffering from hereditary spherocytosis. Hereditary sphereocytosis is an autosomal dominant condition that causes an auto-hemolytic anemia. It is characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped (donut-shaped), and therefore more prone to hemolysis. On blood smear, Howell-Jolly bodies may be seen within red blood cells. Signs and symptoms include anemia, jaundice, and an enlarged spleen (splenomegaly). Acute cases can cause hypoxia through anemia and acute kernicterus through hyperbilirubinemia, particularly in newborns. Most cases can be detected soon after birth. The number of immature red blood cells (reticulocyte count) will be elevated. Hereditary spherocytosis is caused by a variety of molecular defects in the genes that code for spectrin (alpha and beta), ankyrin, band 3 protein, protein 4.2, and other erythrocyte membrane proteins. Mutations in ankyrin are the most common. Educational Objective: Hereditary spherocytosis is caused by mutations in the ankyrin and spectrin genes. Ankyrin mutations are the more common of the two. |
Approved | Approved::Yes |
Keyword | WBRKeyword::Hematology, WBRKeyword::Genetics, WBRKeyword::Hereditary spherocytosis, WBRKeyword::Spherocytosis, WBRKeyword::RBC |
Linked Question | Linked:: |
Order in Linked Questions | LinkedOrder:: |