Disorders of Hemoglobin Flashcards
2 main categories of hemoglobin disorders?
structure variants
thalassemias
Consequences of structural abnormalities?
sickling instability altered O2 affinity increased susceptibility to oxidation to methemoglobin underproduction
How to diagnose globin problem in lab?
Hb electrophoresis
HPLC (high performance liquid chromatography)
What to patients with sickle cell trait gain?
protection against malaria
What is the extent of HbS polymerization dependent on?
time & concentration
List some clinical settings that predispose to sickling
hypoxia acidosis dehydration cold temp infections
What is the lifespan of a sickled cell?
20 days
Major effects of RBC sickling
chronic hemolysis and microvascular occlusion with resultant tissue hypoxia and infarction
When do the effects of sickle cell first show up after birth?
10-12 weeks of age
Main clinical manifestations (14)
severe anemia acute pain crisis auto-splenectomy acute chest syndrome strokes aplastic crisis splenic sequestration crisis megaloblastic anemia growth retardation bony abnormalities renal dysfunction leg ulcers infections cholelithiasis
What is most common cause of death in sickle cell?
acute chest syndrome
What is the main cause for aplastic crisis in sickle cell?
parvovirus B19 infection
What happens during a splenic sequestration crisis?
acute pooling of blood in spleen
drop in Hb
potential for hypovolemic shock
Why does megaloblastic anemia cocur in Sickle Cell?
increased folate consumption because of chronic erythroid hyperproliferation
Lab findings in sickle cell
sickeld cells, target cells, polychromasia increased reticulocytes chronic anemia increased bilirubin post splenectomy changes in adults
What can happen to the kidneys in pts w/sickle cell trait?
sub clinical damage
What is Hemoglobin SC disease?
sickling disorder
HbC form glu to lys substitution
milder than SS usually
What is HbS/Beta thalasemia?
hetero HbS with trans beta thalassemia allele
asymptomatic to SS like
HbS>HbA
What is a thalassemia?
inherited disorder characterized by decreased production of structurally normal globin chains
Distribution of beta thal?
mediterranean, middle east, some parts of india and pakistan, SE asia
distribution of alpha thal?
africa, mediterranean, middle east, SE asia
Features of thalassemai?
microcytic, hypochromic anemias of varying severity
Beta-Thal major features
absense in beta chain production on both beta alleles
severe anemia
bizarre red cell morphology
transfusion dependence
hybrid of hemolytic anemia and ineffective erythropoiesis
Problems in inadequately transfused beta thal major?
stunted growth mongoloid facies/bony abnormalities/frontal bossing wasting hyperuricemia HSM infections folate defic death in childhood
