Anaemia Flashcards
Definition anaemia
Haemoglobin (Hb) concentration falls below defined level (outside normal range) - Units of Hb are g/L
Causes:
Decrease red blood cells (RBCs)
Decrease Hb content (diagnostic criterion)
Altered Hb does not carry sufficient O2
Symptoms
- Lethargy
- Shortness of breath
- Palpitations
- Headache
Often non-specific: worse if acute onset
Signs:
Pallor, pale conjunctivae
Tachypnoea
Tachycardia
Koilonychia
Spoon shaped nails
Iron deficiency
5 Broad Causes
Bleeding
Deficiency in necessary components: Iron, B12, folic acid
Haemolytic: Increased red cell destruction & shortened RBC lifespan
Bone Marrow Dysfunction / Infiltration
E.g. Aplastic anaemia
Poor O2 Utilisation / Carriage
Classification
Size of red cell
Acute or chronic
Underlying aetiology
Iron Deficiency
A range of causes
Bleeding (esp. occult)
Nutrition
Increased Requirements
Confirm with iron studies:
Ferritin
Fe, Transferrin, Saturation
Diagnostic Tests for Iron
Serum Ferritin
Storage form of iron
Low = iron deficient (high = iron overload or reactive)
Serum Iron
Labile so reflects recent intake of iron
Serum Transferrin
Carrier molecule for iron
Homeostatically goes up if iron deficient
Similar to total iron binding capacity (TIBC)
Percent Transferrin Saturation
Sensitive measure of iron status
Low = iron deficient
Causes of Iron Deficiency in UK
Bleeding
- Menstrual - Occult GI Malignancy - GI peptic ulceration
Unlikely to be iron deficient from diet alone
- Vegan/vegetarian - Malabsorption, e.g. coeliac disease and Crohn’s
Increased Requirements - pregnancy
Categorise by size
Mean Corpuscular Volume
Normally about 80-100fL
Microcytic (Small)
Iron deficiency
Inherited disorders of haemoglobin (thalassaemia)
Macrocytic (Large)
B12 and folate deficiency
Myelodysplasia
Normocytic (Normal)
Blood Film benefits
Easy
Quick
Useful
Red cells last 100 days in the circulation
Reticulocyte Count
Represents RBC production rate by marrow
Low if bone marrow infiltrated
Low during precursor deficiencies (e.g. iron)
High in haemolysis
High in chronic bleeding
If in normal range when anaemic, bone marrow is not responding appropriately
Can be used to monitor progress of treatment
Measured by flow cytometry that counts cells with nucleic acids (i.e. RNA) or using a specific stain and microscopy
Blood Film Features
– Iron Deficiency
Hypochromia
Microcytosis
Pencil Cells
Target Cells
History when anaemia suspected
GI Symptoms:
- Dyspepsia
- Change in Bowel Habit (?melaena)
- Weight Loss
Menstrual History
Dietary history
Travel History
Ethnic Origin
Family History
Megaloblastic Anaemia
Macrocytic (MCV > 100)
Due to deficiency of: Vitamin B12 & Folate
Required for DNA Large RBCs Sufficient iron for Hb Sufficient precursors for cell growth Insufficient precursors for cell division
B12 Deficiency
Dietary - strict vegans
Pernicious Anaemia
Autoimmune – parietal cell loss
Deficiency of intrinsic factor
Malabsorption:
Post gastric / ileal surgery
Crohn’s disease
Folate Deficiency
Dietary – common
Malabsorption: Coeliac & Crohn’s disease
Excess Utilisation: Chronic haemolysis & Pregnancy
Alcohol
Drugs
Phenytoin
Methotrexate
Anaemia of Chronic Disease
Most common form of anaemia in hospitalised patients
Common causes:
Chronic inflammation & chronic infection e.g. TB
Auto-immune conditions e.g. rheumatoid arthritis
Cancer
Anaemia of Chronic Disease mechanism
Poor Utilisation of Iron in Body
Iron is stuck in macrophages of the reticuloendothelial system and cannot be mobilised into the early erythroblasts
Dysregulation of Iron Homeostasis
Decreased transferrin
Increased hepcidin
Impaired proliferation of erythroid progenitors
Blunted response to Epo (erythropoietin)
Iron is unavailable
Sickle Cell Anaemia
Point mutation in beta globin gene causing HbS (sickle Hb)
RBCs turnover = approx 20 days due to haemolysis
Sickle cell crisis
Triggered by low blood O2 level
Vaso-occlusive
Ischaemia, pain, necrosis and often organ damage
Management – Analgesics, hydration, transfusion
Genetic, autosomal recessive
Sub-Saharan Africa, shortened life expectancy
Sickle cell anaemia mechanism
Sickle cell disease = Mutated Sickle Haemoglobin (HbS)
forms long filamentous strands
insoluble at low O2 tension
RBCs become inflexible + spiky -> crisis
Sickle cell trait = heterozygous for HbS and HbA,
much lower risk of sickling and crisis
resistant to malaria infection
Thalassaemia
Insufficient Hb production
Due to altered Hb gene expression
Inherited autosomal recessive
Clinical features:
enlarged spleen, liver, and heart
bones may be misshapen
Alpha versus Beta thalassaemia
Intermedia versus major
Life-long transfusions
Thalassaemia - history & diagnosis
Family history
Trait vs disease
Distribution as per malaria
FBC – characteristic indices
Microcytic
Hypochromic
Hb electrophoresis
Blood Film
Bone Marrow Infiltration
Leukaemia
Non-specific symptoms
Bone marrow failure
Lymphoma
Lymphadenopathy
Weight loss
Myeloma
Anaemia
Hypercalcaemia
Renal Failure
Bone Marrow obtained from iliac crest:
aspirate film for morphology of cells
trephine biopsy for histological sections
Acute anaemia management
When to transfuse:
Acute > chronic
Be guided by symptoms rather than Hb level
Can the patient replenish the blood cells?
If not, then transfuse for symptoms (usually <90g/L)
Acute on chronic haemorrhage
Haematemesis (vomiting blood)
Melaena (darkened stools)
