Haematology (anaemia) Flashcards
What is anaemia defined as in children?
o Neonate: Hb <14
o 1-12 months: Hb<10
o 1-12 years: Hb <11
How does foetal and adult haemoglobin differ?
o Foetal Hb (HbF) is made of two alpha units and two gamma units- it has a higher affinity for oxygen than adult Hb
o Adult Hb (HbA) is made of two alpha unity and two beta units
o HbF is gradually replaced by HbA in the first year of life- by 1, the percentage of remaining HbF is very low
• At birth (term)- Hb is high (14-21.5g/dL) to compensate for the low O2 concentration in the foetus, Hb falls over the first few weeks, due to RBC production, and reaches 10g/dL at 2 months of age
What are the causes of IDA?
o Inadequate intake
o Malabsorption
o Blood loss (rare)
additional iron is required for the increase in blood
volume accompanying growth and to build up the child’s iron stores
• Iron can come from breast milk (50% absorbed – by far the best source)- may come from a delay in weaning
• Iron is best absorbed with vitamin c and without tannin from tea (or red wine!)
What are the clinical features of IDA?
not present until below 6-7 g/dl
Lethargy
Feed slowly
Pale- conjunctiva, tongue or palmar creases
How is IDA diagnosed?
microcytic, hypochromic anaemia (low MCV & MCH) and low serum ferritin
What are the dietary sources of iron?
o Foods to avoid in excess in toddlers Cow’s milk Tea- tannin inhibits iron uptake High fibre foods- phytates inhibits iron absorption o High in iron Red meat Liver/kidney Oily fish o Average iron Pulses, beans & peas Fortified breakfast cereals with added vitamin C Wholemeal products Dark green vegetables- broccoli, spinach Dried fruit- raisins, sultanas Nuts & seeds- cashews or peanut butter
What are the main causes of haemolytic in children?
o Red cell membrane disorders (e.g. hereditary spherocytosis) o Red cell enzyme disorders (e.g. glucose-6-phosphate dehydrogenase deficiency) o Haemoglobinopathies (abnormal haemoglobins, e.g. β-thalassaemia major, sickle cell disease).
What does haemolysis from increased red cell breakdown lead to?
o Anaemia
o Hepatomegaly and splenomegaly
o Increased blood levels of unconjugated bilirubin
o Excess urinary urobilinogen.
What are the diagnostic clues for haemolysis?
o Raised reticulocyte count on the blood film- ‘polychromasia’ as the reticulocytes have a characteristic lilac colour
o Unconjugated bilirubinaemia and increased urinary urobilinogen
o Abnormal appearance of the red cells on a blood film e.g. spherocytes, sickle shaped or very hypochromic
o Positive direct antiglobulin test- only if an immune cause, as this test identifies antibody-coated RBCs.
o Increased RBC precursors in the bone marrow
What is hereditary spherocytosis?
1 in 5000 in caucasians
AD inheritance (25% no family history)
Mutations in genes for proteins of the red cell membrane- mainly spectrin, ankyrin or band 3
Red cell loses part of membrane when passing through spleen- reduction in SA:V
Cells become spheroidal, making them less deformable than normal and leads to their destruction in the microvasculature of the spleen
What are the clinical features of hereditary spherocytosis?
o Jaundice: usually develops during childhood, but may be intermittent, may cause severe haemolytic jaundice in the first few days of life
o Anaemia: presents in childhood with mild anaemia, but the Hb level may transiently fall during infections
o Mild to moderate splenomegaly: depends on the rate of haemolysis
o Aplastic crisis: uncommon, transient (2-4weeks), caused by parovirus B19 infection
o Gallstones: due to increased bilirubin excretion
What are the investigations for hereditary spherocytosis?
Blood film
osmotic fragility or dye binding tests
direct antibody test in the absence of a family history of hereditary spherocytosis- rule out autoimmune haemolytic anaemia
What is the management for hereditary spherocytosis?
oral folic acid, as they have a raised requirement secondary to their increased RBC production
Splenectomy- poor growth, symptoms of anaemia- usually deferred until >7 because of post-op sepsis risk
Vaccinations- Hib, meningitis C, S. pneumoniae
Life long daily oral penicillin prophylaxis
• Aplastic crisis from parovirus B19 infection usually requires one or two blood transfusions over 3-4 weeks-
when no RBC are produced
What is glucose-6-phospahte dehydrogenase deficiency (G6PD)?
commonest red cell enzymopathy
X-linked
• G6PD is the rate-limiting enzyme in the pentose phosphate pathway, it is essential for preventing oxidative damage to red cells, therefore RBCs lacking G6PD are susceptible to oxidant-induced haemolysis
What are the clinical features of G6PD deficiency?
o Neonatal jaundice- onset is usually in the first 3 days of life o Acute haemolysis precipitated by: Infection- most common certain drugs fava beans- broad beans naphthalene in mothballs. Fever, malaise, dark urine Hb falls rapidly- may drop below 5 g/dl over 24–48 h
What occurs between episodes in G6PD deficiency?
almost all patients have a completely normal blood picture and no jaundice or anaemia
diagnosis is made by measuring G6PD activity in red blood cells
during a haemolytic crisis, G6PD levels may be misleadingly elevated due to the higher enzyme concentration in reticulocyte
a repeat assay is then required in the steady state to confirm the diagnosis
What are haemoglobinopathies?
red blood cell disorders which cause haemolytic anaemia because of reduced or absent production of HbA (α- and β-thalassaemias) or because of the production of an abnormal Hb e.g. sickle cell disease
• α-Thalassaemias- caused by deletions (occasionally mutations) in the α-globin gene
• β-Thalassaemia and sickle cell disease are caused by mutations in the β-globin gene
• Clinical manifestations of the haemoglobinopathies affecting the β-chain are delayed until after 6 months of age when most of the HbF present at birth has been replaced by adult HbA
