Anaemia

• Anaemia can be classified based on the mean cell volume (MCV):

  • Low MCV = microcytic anaemia
  • Normal MCV = normocytic anaemia
  • Raised MCV = macrocytic anaemia
• Causes of microcytic anaemia:

  • Thalassaemia
  • Iron deficiency anaemia - most common
  • Sideroblastic anaemia
• Causes of iron deficiency anaemia:

  • Increased requirement - pregnancy and lactation
  • Increased loss - GI bleeding
  • Decreased uptake - dietary deficiency and malabsorption
• Symptoms of iron deficiency anaemia:

  • Fatigue
  • Dyspnoea
  • Light-headedness
  • Nausea
  • Pica - unusual dietary cravings
• Signs of iron deficiency anaemia on examination:

  • Glossitis
  • Koilonychia
  • Angular stomatitis
  • Conjunctival pallor
• Iron studies in the context of IDA:

  • Gold standard is serum ferritin - low ferritin means a depletion of iron stores (ferritin will be normal in thalassaemia)
  • Serum iron - tends to be low
  • Total iron binding capacity - typically normal or high
• Investigations to find the cause of iron deficiency anaemia:

  • Coeliac screening - TTG
  • Urinalysis
  • Upper and lower GI endoscopy
  • Iron studies
• Treatment of IDA is with ferrous sulfate - continue for 3 months after the anaemia is corrected

  FBC should be checked after 2-4 weeks to assess the person's response to iron treatment
• Consider a blood transfusion when Hb is less than 80 g/L or the patient is haemodynamically compromised
• Causes of normocytic anaemia:

  • Acute blood loss
  • Anaemia of chronic disease - usually CKD due to inadequate erythropoietin
  • aplastic anaemia
  • Haemolytic anaemia
  • Sickle cell anaemia
• Anaemia of chronic disease is a functional iron deficiency whereby the supply of iron for erythropoiesis is inadequate despite apparently normal cellular iron stores - serum ferritin will be high
• Haemolytic anaemia:

  • Normocytic anaemia
  • Premature destruction of RBC - bone marrow cannot compensate
  • Increased reticulocyte count
  • Raised unconjugated bilirubin
  • Raised LDH - high cell turn over
  • Extravascular haemolysis is most common - usually in the spleen
  • Signs - jaundice, splenomegaly
• Macrocytic anaemia can be megaloblastic (presence of megaloblasts in the bone marrow) or normoblastic
• Causes of megaloblastic macrocytic anaemia:

  • B12 deficiency
  • Folate deficiency
• Megaloblasts are immature red cells with large nuclei - B12 and folate deficiency leads to abnormal DNA synthesis and impaired cell maturation - immature cells with abnormally large nuclei
• Causes of normoblastic macrocytic anaemia:

  • Alcoholism
  • Hypothyroidism
  • Liver disease
  • Reticulocytosis - large amount of large immature RBC - usually from haemolytic anaemia
  • Medications - azathioprine, fluorouracil
• • Parietal cells in the gastric epithelium secrete intrinsic factor
  • intrinsic factor binds to vitamin B12 - binds to receptors within the terminal ileum where it is absorbed
• Causes of B12 deficiency:

  • Inadequate intake - strict vegetarians and vegans (found mostly in meat and dairy products)
  • Inadequate intrinsic factor - pernicious anaemia, gastrectomy
  • Malabsorption - Crohn's disease
  • Inadequate release of B12 from food - gastritis and alcohol abuse
• Symptoms of B12 deficiency:

  • Neurological - peripheral neuropathy, subacute degeneration of the cord, focal demyelination
  • Psychiatric features - depression, personality change and memory loss
  • Serum concentration of cobalamin = B12
  • Increased serum levels of homocysteine and methylmalonic acid
• Management of B12 deficiency:

  • Neurological involvement = 1mg IM hydroxocobalamin on alternate days until no further improvement and then every 2 months
  • No neuro involvement = 1mg IM hydroxocobalamin three times a week for 2 weeks and then every 3 months
  • Diet related = oral cyanocobalamin or twice yearly 1mg IM hydroxocobalamin
• If B12 and folate deficient, B12 must be corrected first to avoid neurological complications
• Folate (vitamin B9) is an important molecule which acts as a cofactor in amino acid metabolism and DNA/RNA synthesis
• Causes of folate deficiency:

  ·       Inadequate dietary intake

  ·       Malabsorption (coeliac, crohns)

  ·       Increased requirement (pregnancy, malignancy)

  ·       Increased loss (chronic liver disease)

  ·       Anti-convulsant medication

  ·       ETOH abuse

  Increased serum homocysteine but normal serum methylmalonic acid
• Management of folate deficiency:

  • Oral folic acid 5mg OD for 4 months - long term if underlying cause is persistent
• Possible clinical findings in anaemia include:

  • Pallor (e.g. general pallor or conjunctival pallor)
  • Rapid or irregular heartbeat on cardiac auscultation
  • Enlarged liver or spleen on palpation (consider lymphoma or leukaemia with splenomegaly)
  • A pelvic or rectal exam may be indicated to assess for blood loss
• Any patient over 40 with iron deficiency anaemia requires an upper and lower gastrointestinal endoscopy.
• Normocytic anaemias:

  • The size of RBCs isn't altered, anaemia usually due to haemolysis or underproduction
  • Reticulocyte count differentiates the two - high reticulocyte count suggests there is haemolysis