Microcytic Hypochromic Anaemia Flashcards by raniya robb

what is the definition of microcytic hypochromic anaemia?

low Hb
low MCV <0.8
hypochromic = low uptake of stain

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the causes of microcytic. hypochromic anaemia are associated with what?

reduced haemoglobin production

causes smaller cells and less uptake of stain

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what causes are due to problems producing the haem group?

iron deficiency anaemia

anaemia of chronic disease

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what causes are due to problems producing the porphyrin ring?

sideroblastic anaemia

lead poisoning (cabot rings)

pyridoxine responsive anaemia

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what causes are due to problems producing the globin chains?

thalassemia

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how does iron deficiency anaemia develop?

due to there being insufficient iron to produce haemoglobin

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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

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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

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what investigation results would indicate iron deficiency anaemia?

FBC = low Hb / reticulocytes

iron studies = low iron, low ferritin and low transferrin saturation

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what does ferritin levels indicate?

iron stores

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what does transferrin levels indicate?

transported iron

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what iron replacement should be given in iron deficiency anaemia?

200mg ferrous sulphate or fumerate

should be given for minimum of 3 months

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what are the common side effects of iron replacement?

nausea
black stool
diarrhoea
constipation

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if response to iron replacement is not adequate, what should you consider?

poor compliance
wrong diagnosis
continued activity of underlying cause

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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

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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

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when should sideroblastic anaemia be considered?

microcytic hypochromic anaemias not responding to treatment

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what is shown in investigations in sideroblastic anaemia?

marrow biopsy = ring sideroblasts

microcytic anaemia with high iron, ferritin and transferrin

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how is sideroblastic anaemia treated?

treat underlying cause and regular blood transfusions

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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

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in general, what populations are thalassemias more common in?

african, asian and southern european populations

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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

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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