Microcytic Hypochromic Anaemia Flashcards
what is the definition of microcytic hypochromic anaemia?
low Hb
low MCV <0.8
hypochromic = low uptake of stain
the causes of microcytic. hypochromic anaemia are associated with what?
reduced haemoglobin production
causes smaller cells and less uptake of stain
what causes are due to problems producing the haem group?
iron deficiency anaemia
anaemia of chronic disease
what causes are due to problems producing the porphyrin ring?
sideroblastic anaemia
lead poisoning (cabot rings)
pyridoxine responsive anaemia
what causes are due to problems producing the globin chains?
thalassemia
how does iron deficiency anaemia develop?
due to there being insufficient iron to produce haemoglobin
what are common causes of low iron?
chronic blood loss = menorrhagia, GI bleeds
malabsorption = coeliac disease, post gastrectomy
poor dietary intake = vegan or vegetarian
infection = hookworm
what are specific signs of iron deficiency anaemia?
nails = koilonychias
mouth = angular stomatitis, atrophic glossitis
throat = post cricoid webs, plummer vinson syndrome in PM women
what investigation results would indicate iron deficiency anaemia?
FBC = low Hb / reticulocytes
iron studies = low iron, low ferritin and low transferrin saturation
what does ferritin levels indicate?
iron stores
what does transferrin levels indicate?
transported iron
what iron replacement should be given in iron deficiency anaemia?
200mg ferrous sulphate or fumerate
should be given for minimum of 3 months
what are the common side effects of iron replacement?
nausea
black stool
diarrhoea
constipation
if response to iron replacement is not adequate, what should you consider?
poor compliance
wrong diagnosis
continued activity of underlying cause
in iron deficiency anaemia, when should you refer for further investigation (OGD +/- colonoscopy)?
iron deficiency anaemia with dyspepsia all men with unexplained IDA IDA with rectal bleeding all women not menstruating with unexplained IDA not responding to treatment
what is the name of rare type of anaemia that can be an X linked condition or secondary to chemotherapy or anti TB drugs and lead poisoning?
sideroblastic anaemia
*ineffective erythropoiesis will drive iron absorption and deposition in organs other than liver
when should sideroblastic anaemia be considered?
microcytic hypochromic anaemias not responding to treatment
what is shown in investigations in sideroblastic anaemia?
marrow biopsy = ring sideroblasts
microcytic anaemia with high iron, ferritin and transferrin
how is sideroblastic anaemia treated?
treat underlying cause and regular blood transfusions
what is thalassemia?
a group of conditions in which there is defective production of the globin chains found in haemoglobin - normal chains, not enough of them!
this defective production results in accumulation of unbalanced haemoglobin chains in RBC - leads to cells being small and hypochromic and susceptible to premature haemolysis
in general, what populations are thalassemias more common in?
african, asian and southern european populations
briefly describe the genetics behind alpha thalassemia?
there are four a globin genes on chromosome 16
a thalassemia is caused by deletion mutation in any of these genes
due to alpha globin being present in all haemoglobin subtypes, the production of all types of Hb will be affected
what occurs in a thalassemia trait?
one or two alpha genes missing
what is the characteristics of a thalassemia trait?
asymptomatic carrier state, no treatment needed
microcytic, hypochromic red cells with mild anaemia
how can a thalassaemia trait be distinguished from iron deficiency?
ferritin will be normal
what happens in HbH disease?
three copies of the a gene are lost so the production of normal haemoglobin is significantly reduced
this results in increased production of abnormal haemoglobin (HbH)
what are the symptoms of HbH disease?
general anaemia symptoms
symptoms of chronic haemolysis = jaundice, leg ulcers, hepatosplenomegaly
(other = growth retardation, gallstones, iron overload)
what does HbH look like on FBC, iron studies and film?
FBC = low Hb, MCV and MCH
Iron = normal or increased iron / ferritin
film = heinz bodies, target cells
what is diagnostic of HbH?
HPLC - high performance liquid chromatography
- low HbA, HbA2 and HbF
- high HBH
how is HbH treated?
folic acid supplementation - to support increased erythropoiesis
mild - intermittent transfusion
severe - regular transfusions +/- splenectomy
what is Hb barts hydrops fetalis?
all 4 copies of a gene are mutated
as a result of no functional alpha haemoglobin, the only type is Hb Barts
results in hydrops fetalis and IUD
briefly describe the genetics behind B thalassemia?
B thalassemia develops due to point mutation in beta globin gene on chromosome 11
this can result in either reduced (B+) or absent (B0) production of B globin
due to B chain only being present in HbA, there will be reduced HbA production and a compensatory increase in production of other types of haemoglobin
what is B thalassemia trait and what are the clinical features?
the trait is found when patients are heterozygous for the mutation (one normal copy)
asymptomatic
what is the biochemical features of B thalassemia trait?
FBC: mild microcytic, hypochromic anaemia
HPLC: raised HbA2 diagnostic
what is B thalassemia intermedia?
the less severe form of clinically apparent B thalassemia
how does B thalassemia intermedia present?
mild to moderate anaemia +/- splenomegaly
how is B thalassemia intermedia managed?
not usually very symptomatic
may require intermittent transfusions
how does b thalassemia major occur?
patient is homozygous for B0 (absent B chains)
when and how does B thalassemia major normally present?
usually within first year of life
failure to thrive
severe anaemia
extra medullary haematopoiesis: hepatosplenomegaly, skull bossing, multiple organ damage
what does FBC, iron studies and blood film show in B thalassemia major?
FBC = low Hb and MCV
iron studies = normal
film = target cells, nucleated RBCs (normally not nucleated)
what does HPLC show in B thalassemia major?
very high HbF
high HbA2
low HbA
what is shown on skull XR in B thalassemia major?
hair on end sign
how is B thalassemia major managed?
life long transfusions
folate supplementation
life long transfusions + iron chelators (deferiprone)
+/- splenectomy
what is the main mortality of B thalassemia major?
iron overload
what are the consequences of iron overload?
endocrine dysfunction = impaired growth and pubertal development, diabetes, osteoporosis
cardiac disease = cardiomyopathy, arrhythmias
liver disease = cirrhosis, hepatocellular cancer
how is iron overload prevented?
use iron chelating drugs (bind to iron which is then excreted)
what are other consequences of life long transfusions (except iron overload)?
viral infection = HIV, hep B and C
alloantibodies = hard to crossmatch
transfusion reactions
increased risk of sepsis (bacteria like iron)
give an example of the normal production of abnormal globin chains?
variant haemoglobin eg HbS
how does sickle cell trait (HbAS) occur?
one normal, one abnormal B gene
what are the features of sickle cell trait (HbAS)?
asymptomatic carrier state
may sickle in severe hypoxia eg high altitude, under anaesthesia
blood film normal
mainly HbA, HbS <50%
how does sickle cell anaemia (HbSS) occur?
two abnormal genes
what type of haemoglobin predominates in HbSS?
HbS >80%, there is no HbA
what is a sickle crises?
episode of tissue infarction due to vascular occlusion - symptoms depend on site and severity and pain may be extremely severe
what can precipitate a sickle cell crises?
hypoxia dehydration infection cold exposure stress / fatigue
how is sickle cell crises treated?
opiate analgesia hydration rest oxygen antibiotics if infection red cell exchange transfusion in severe crises eg chest crisis or stroke
other than sickle cell crises, what are the other consequences of HbSS?
chronic haemolysis = shortened RBC lifespan
sequestration of sickled RBCs in liver and spleen
hyposplenism due to repeated splenic infarcts
how is HbSS managed long term?
hyposplenism - reduce risk of infection by prophylactic penicillin and vaccinations
folic acid supplementation
hydroxycarbamide to reduce severity of disease
regular transfusion in select cases
