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Sickle Cell Disease (SCD) - Coggle Diagram
Sickle Cell Disease (SCD)
Genetic Details
A genetic point mutation (missense) in β-globin:
Replacement of one glutamate amino acid with a valine amino acid
Hemoglobin consists of 6 protein subunits: 4 α-globin and 2 β-globin.
Hemoglobin B gene mutations provide instructions for making other versions of β-globin.
Hemoglobin S(HbS; sickle hemoglobin):
Affect the quantity of β-globin and distorting erythrocytes into a sickle shape
Homozygous form
Inherited in an autosomal recessive pattern where each parent carries one copy of the mutated gene
Sickle Cell Disease (SCD)
Heterozygous form
Sickle cell trait (HbAS): Child inherits HbS from one parent and a normal hemoglobin (HbA) from the other
Carrier
Pathophysiologic Etiology
Decrease in intracellular pH
Reduce the oxygen affinity of hemoglobin
Increase the quantity of deoxygenated HbS at any oxygen tension
Inflammation in the microcirculation
Adhesion of leukocytes to activated endothelial cells
Sluggish blood flow
Slow erythrocyte transit times
Intracellular dehydration
Increase mean cell hemoglobin concentration (MCHC)
Increase sickling
Damages the red blood cell (RBC) structure
Polymerization of sickled hemoglobin
Sickled erythrocyte stiffens
HbS molecules stack into polymers that starve and damage tissues
RBC membrane damages and other local factors, such as inflammation or vasoconstriction
Decrease blood flow or arrest red cells through the microcirculation
Microvascular obstruction
Erythrocyte membrane derangement
Changes in ionic flow
Damaged cells are converted to end-stage, nondeformable or stiff and irreversibly sickled cells
Ischemic tissue damage
Cycles of deoxygenation and oxygenation
HbS molecule to polymerize and stiffen
Treatments
Immediate correction of acidosis and dehydration with appropriate intravenous fluid
RBC transfusions
Preventing infection
The use of prophylactic antibiotics (Penicillin)
Vaccination
Seek immediate medical attention in the event of fever
Proper pain management
Aggressive management of fever
Genetic counseling and psychologic support for the child and family
Diagnostic Tests
Sickle solubility test
Confirms the presence of HbS in blood
Hemoglobin electrophoresis
Amount of HbS in erythrocytes
Prenatal diagnosis
Chorionic villus sampling as early as 8 to 10 weeks of gestation
Amniotic fluid analysis at 15 weeks of gestation
New born screening
Causative factor
Parents' hematologic history:
Both parents carry at least one copy of the mutated gene
Risk Factors
Dehydration
Constricting clothes
Acidosis
Infection
Exposure to cold
Fever
Common Findings
Hyperhemolytic crisis
An accelerated rate of RBC destruction. Rare. May associate with certain drugs or infections.
Sequestration crisis
Large amounts of blood with massive large amounts of sickle red cells become pooled in the spleen
Aplastic crisis
A result of a viral infection that causes a transient cessation in RBC production resulting in acute anemia
Vaso-occlusive crisis (pain crises)
Severe pain in affected areas due to hypoxic injury and infarction
General manifestations of hemolytic anemia
Jaundice
Irritability
Fatigue
Pallor