Thalassemias Flashcards
what does thalassaemia result in?
microcytic anaemia
what is the consequence of accumulation of globin chains?
ineffective erythropoiesis + haemolysis
what is the cause of alpha thalassaemia?
deletion of alpha genes from chromosome 16
alpha chains are present in which forms of Hb?
HbA, HbA2 and HbF
what is the genes of someone unaffected by alpha thalassaemia?
4 normal α genes (αα/αα)
how many genes are missing in alpha thalassemia trait?
one or two genes missing
what are the genes of someone with alpha thalassaemia trait?
α+/α (-α/αα)
α0/ α (–/αα)
α+/α+(-α/-α)
what are the clinical features of someone with alpha thalassemia trait?
Asymptomatic
Microcytic, hypochromic red cells with mild anaemia
what is the disease associated with only one alpha gene left?
HbH disease
what are the genes of someone with HbH disease?
α0/α+(–/-α )
what is the characteristic feature of HbH disease?
formation of HbH
what is the pathophysiology of HbH disease?
Excess β chains form tetramers (β4) called HbH which can’t carry oxygen
what are the clinical features of HbH disease?
Severe
Anaemia - moderate anaemia to transfusion dependent
Splenomegaly
Jaundice - Haemolysis, Ineffective erythropoiesis
what can be seen histologically in HbH disease?
Red cell inclusions of HbH
what is the anaemia associated with HbH?
microcytic
what are the MCV and MCH in HbH?
very low
what is the disease associated with no functional alpha genes?
Hb Barts hydrops fetalis
what are the genes of someone with Hb Barts hydrops fetalis disease?
α0/α0 (–/–)
what is the characteristic feature of Hb Barts?
Hb (y4)
what are the haemoglobin types found in Hb Barts at birth?
Hb Barts (γ4) and HbH (β4)
what are the clinical features of Hb Barts Hydrops Fetalis?
Severe anaemia Cardiac failure Growth retardation Severe hepatosplenomegaly Skeletal and cardiovascular abnormalities Almost all die in utero
what does the blood film in Hb Barts Hydrops Fetalis?
numerous nucleated RBCs
what is beta thalassaemia?
Disorder of beta chain synthesis
which haemoglobin is affected in beta thalassaemia?
HbA (α2β2)
what are are the genes of someone with B thalassaemia trait?
(β+/β or β0/β)
what are are the genes of someone with B thalassaemia intermedia?
(β+/β+ or β0/β+)
what are are the genes of someone with B thalassaemia major?
(β0/β0)
what are the clinical features of B thalassaemia trait?
Asymptomatic
No/Mild anaemia
what are the MCV/MCH of B thalassaemia trait?
low MCV/MCH
what are the clinical features of B thalassaemia intermedia?
Moderate severity
what is the management of B thalassaemia intermedia?
requires occasional transfusion
what are the clinical features of B thalassaemia major?
Severe Presents 6-24 months Pallor, failure to thrive Hepatosplenomegaly Skeletal changes Organ damage Cord compression
what is the haemoglobin analysis of B thalassaemia major?
Mainly HbF
Minimal HbA
what is the management of B thalassaemia major?
Regular transfusion programme to maintain Hb at 95-105g/l
Bone marrow transplant
what are the risks of blood transfusion?
Iron overload
Viral infection - HIV, Hepatitis B and C
Transfusion reaction Increased risk of sepsis
