Microcytic Anaemia Flashcards
What is the Hb criteria for anaemia for males?
<130g/L
What is the Hb criteria for anaemia for females?
<120g/L
When are Hb and Hct not good markers for anaemia?
when its not in steady state eg rapid blood loss
or in haemodilution
How is the response to anaemia measured?
reticulocyte count
What leads to a microcytic anaemia?
shortage in globin or heme (porphyrin ring and iron)
What is microcytic anaemia?
low MCV
hypochromatic
What causes a microcytic anaemia?
Heme deficiency - iron deficiency + anaemia of chronic disease
porphyrin ring synthesis - lead poisoning, pyridoxine responsive anaemia, sideroblastic anaemia
globin deficiency - thalassaemia
What is the role of iron?
oxygen transport - Hb and myoglobin
electron transport - mitochondrial production of ATP
What is iron stored in in the liver?
Ferritin
What is iron stored in in the body?
haemaglobin
What is circulating iron bound to?
transferrin
What does transferrin pass iron onto?
bone marrow macrophages that feed it to red cell precursors
What are the properties of transferrin?
protein with two binding sites for iron atoms
transports iron from donor tissues (macrophages, hepatocytes + intestinal cells) to tissues expressing transferrin receptors
How do you measure iron supply?
% saturation of transferrin with iron
How do you measure iron storage?
serum ferritin
How does ferritin react to acute inflammation/disease?
increases so binds lots of iron so the bacteria cannot feed on the iron
What are the causes of iron deficiency anaemia?
menorrhagia
GI - tumours, ulcers, NSAIDs
haematuria
coeliac disease - not absorbing enough from proximal small bowel
How many mg a day do you need iron intake wise?
1mg a day
What ml of blood and mg of iron do you lose on average each menstrual cycle?
30-40ml
15-20mg iron
What are the consequences of iron deficiency?
epithelial changes - dry skin and koilonychia of nails
microcytic anaemia
iron deficient erythropoesis
exhaustion of iron stores
What are the different variants of Hb?
HbA
HbF
HbA2 - 2 aplha 2 delta
What chromosome are alpha genes found? How many per chromosome?
chromosome 16
2 genes per chromosome 4 per cell
What chromosome are beta genes found? How many per chromosome?
chromosome 11
1 gene per chromosome 2 per cell
What are haemoglobinopathies?
abnormal globin chain synthesis caused by autosomal recessive disorders leading to microcytic anaemias
What are the types of haemoglobinopathies?
thalassaemias
structural haemoglobin variants
What are the two types of thalassaemias?
alpha and beta
What is an alpha thalassaemia?
will result from deletion of 1 alpha or both
i.e. can be reduced chain production or absent chain production
What are the 3 types of alpha thalassaemias?
alpha thalassaemia trait (-a,aa) HbH disease (--,-a) Hydrops foetalis (--,--)
How does Alpha thalassaemia trait present?
asymptomatic
microcytic hypochromatic cells with a mild anaemia
What treatment is required for Alpha thalassaemia trait?
NONE
How is Alpha thalassaemia trait distinguished from iron deficiency anaemia?
ferritin
How does HbH disease present?
more severe
anaemia with very low MCV and MCH
jaundice and splenomegaly
Where is HbH disease common?
SE asia
How is HbH disease treated?
splenectomy
transfusions
folic acid 1mg
What is Hydrops foetalis?
no alpha chain to bind to so tetramers of Hb Barts and HbH produced
most severe form
How does Hydrops foetalis present?
profound anaemia cardiac failure skeletal and CUS abnormalities growth retardation severe hepatosplenomegaly BUT NORMALLY PICKED UP ON ANTENATAL SCREENING AND DIE IN UTERO
What are the types of beta thalassaemia?
b thalassaemia trait (B+/B) or (B0/B)
b thalassaemia intermedia (B+/B+) or (B0/B+)
b thalassaemia major (B0/B0)
What causes beta thalassaemia?
disorder of B chain synthesis, usually caused by point mutations
can be reduced (B+) or absent (B0) B depending on the mutation
What type of Hb does beta thalassaemia affect?
adult Hb - 2 alpha 2 beta
How does b thalassaemia trait present?
asymptomatic
mild/no anaemia
How is b thalassaemia trait tested for?
raised HbA2 in blood
How does b thalassaemia intermedia present?
moderate anaemia - jaundice and splenomegaly
How is b thalassaemia intermedia treated?
transfusion ocassionaly
How does b thalassaemia major present?
severe anaemia
6-24 months as HbF falls
failure to thrive, pallor, hepatomegaly, organ changes and skeletal changes - all due to extramedullary haematopoesis
How is b thalassaemia major treated?
lifelong transfusion
What is the main problem with b thalassaemia major?
iron overload from transfusion
How does iron overload present?
endocrine dysfunction - diabetes, osteoporosis, cardiac disease, liver disease
How do you treat iron overload?
iron chelating drugs - desferioxamine
