The Sickle Cell Anemia is a autosomal recessive disorder caused by a change in the 6 codon of the B-globin gene from A to T, results in a modified hemoglobin structure. The results is Hemoglobin S which polymerizes under low oxigen conditions, causing distortion of red blood cells leading to the associated clinical phenotype.
Thr Pro Glu Glu beta A chain
ACT CCT GAG GAG beta A gene
codon # 4 5 6 7
ACT CCT GTG GAG beta A gene
Thr Pro Val Glu beta A chain
The mutation in the gene coding for the B-chain of hemoglobin results in RBCs assuming a sickle shape when deoxygenated which them precipitate out of circulation and may occlude the microvasculature.
Mutation in both B-chain define the Sickle Cell disease, a single affected chain is Sickle cell trait.
HbS mutation is a single amino acid replacement in B-chain, substitution of normal glutamic acid with Valine. Low oxigen or dehydration precipitates sickling. Heterozygotes (sickle cell trait) are relatively malaria resistant.
Complivation in Homozygotes include aplastic crisis, due to parvovirus B19 infection, autosplecnectomy, inrease risk of encapsulated organism infection, Salmonella osteomyelitis, painful crisis, and splecnic squestration crisis.
Acute chest pain due to occlusion of bone marrow can cause a fat embolus to the lungs, resulting in hypoxemia anf possibly cardiovascular collapse.
8% of African-Americans carry the HbS trait, 0,2 % have the disease.
Sickled cells are crescent-shape RBC.
"Crew cut" in skull x-ray due to marrow expansion from increase erythropoiesis.
New-Born initially asymptomatic owing to high HbF and low HbS
Therapic for SCA include Hydroxyurea and bone marrow transplantation.
Because Ribavirin may cause a hemolytic anemia, it should be avoided in pte with hematologic disorder such as Sickle cell anemia and Thalasemia major.
retrieved from: First Aid for the USMLE step 1 2016, First Aid for Basic Sciences and General Princeples 2012.
Thr Pro Glu Glu beta A chain
ACT CCT GAG GAG beta A gene
codon # 4 5 6 7
ACT CCT GTG GAG beta A gene
Thr Pro Val Glu beta A chain
The mutation in the gene coding for the B-chain of hemoglobin results in RBCs assuming a sickle shape when deoxygenated which them precipitate out of circulation and may occlude the microvasculature.
Mutation in both B-chain define the Sickle Cell disease, a single affected chain is Sickle cell trait.
HbS mutation is a single amino acid replacement in B-chain, substitution of normal glutamic acid with Valine. Low oxigen or dehydration precipitates sickling. Heterozygotes (sickle cell trait) are relatively malaria resistant.
Complivation in Homozygotes include aplastic crisis, due to parvovirus B19 infection, autosplecnectomy, inrease risk of encapsulated organism infection, Salmonella osteomyelitis, painful crisis, and splecnic squestration crisis.
Acute chest pain due to occlusion of bone marrow can cause a fat embolus to the lungs, resulting in hypoxemia anf possibly cardiovascular collapse.
8% of African-Americans carry the HbS trait, 0,2 % have the disease.
Sickled cells are crescent-shape RBC.
"Crew cut" in skull x-ray due to marrow expansion from increase erythropoiesis.
New-Born initially asymptomatic owing to high HbF and low HbS
Therapic for SCA include Hydroxyurea and bone marrow transplantation.
Because Ribavirin may cause a hemolytic anemia, it should be avoided in pte with hematologic disorder such as Sickle cell anemia and Thalasemia major.
retrieved from: First Aid for the USMLE step 1 2016, First Aid for Basic Sciences and General Princeples 2012.
