Haematological Disorders Flashcards
When is HbF very low in healthy children - when is it not?
By age 1
Increased proportions of HbF are indicators of severe inherited disorders of haemoglobin production - haemoglobinopathies
Hb at birth
14-21.5g/dl to compensate for low oxygen concentration in fetus
What happens to Hb after birth
Falls over first few weeks of life, mainly due to reduced red cell production, to 10g/dl at 2 months of age
What happens to Hb after birth in pre-term babies?
It has a steaper fall to a mean of 6.5-9g/dl at 4-8 weeks chronological age
What are the iron, B12 and folic acid stores like in term and preterm infants at birth and after birth?
Iron, B12 and folic acid are adequate at birth in term and preterm babies
However in preterm babies stores of iron and folic acid are lower and are depleted more quickly leading to deficiency after 2-4months if recommended daily intakes are not maintained by supplements
Anaemia value in neonate
Hb less than 14g/dl
Anaemia value in 1-12months old
Hb less than 10g/dl
Anaemia value in 1-12 years
Hb less than 11g/dl
What is red cell aplasia
Complete absence of red cell production
What is ineffective erythropoeisis?
Red cell production is normal/increased rate but differentiation or survival of red cells is defective
What are the main causes of iron deficiency anaemia x3
Inadequate intake (common in infants)
Malabsorption
Blood loss
Which milk is not good for maintaining infant iron levels?
Cows milk because it has a higher iron content than breast milk but only 10% of the iron is absorbed
Therefore infants should not be fed unmodified cows milk
At what Hb level do children become symptomatic with anaemia?
6-7g/dl
How do children with iron deficiency anaemia present?
Pica- eating non-food materials such as soil, chalk, gravel or foam rubber
What are indicators on blood tests of iron deficiency anaemia
Microcytic, hypochromic anaemia (low MCV and MCH)
Low serum ferritin
Management of iron deficiency anaemia in infants?
Increase oral iron intake with supplementation - Sytron or Niferex are best tolerated preparations
Or just increase iron rich foods
What are the 3 main causes of red cell aplasia in children?
1) Diamond-Blackfan anaemia - congenital red cell aplasia
2) Transient erythroblastopenia of childhood
3) Parvovirus B19 infection in children with haemolytic anaemia
Diagnostic features of red cell aplasia x4
Low reticulocyte count despite normal Hb
Normal bilirubin
Negative direct antiglobulin/Coombs test
Absent red cell precursors on bone marrow examination
What is Diamond-Blackfan anaemia?
It is a rare congenital disease of red cell aplasia
Inheritance of Diamond-Blackfan anaemia
20% family history - remaining 80% are sporadic mutations
RPS (ribosomal protein) genes implicated in some cases
Presentation of Diamond-Blackfan anaemia
Most present at 2-3 months of age but 25% present at birth
Features of Diamond-Blackfan anaemia x2
Anaemia
Also congenital abnormalities such as short stature or abnormal thumbs
Treatment of Diamond-Blackfan anaemia x2
Oral steroids
Monthly red cell transfusions for children not responsive to steroids
What is transient erythoblastopenia of childhood?
Red cell aplasia usually triggered by viral infections
Same haemotological features as D-Blackfan anaemia
Prognosis of transient erythroblastopenia of childhood
Always recovers - usually within several weeks (hence differs from d-blackfan)
Inheritance of transient erythroblastopenia of childhood
No family history
When does haemolysis lead to anaemia?
When the bone marrow can no longer increase red cell production to compensate for the premature destruction of red cells
Main causes of haemolytic anaemias in children? What is uncommon children
Intrinsic abnormalities of RBCs (membrane and enzyme disorders and haemoglobinopathies)
Immune haemolysis is uncommon
What does haemolysis from increased RBC breakdown lead to? x4
Anaemia
Hepatomegaly and splenomegaly
Increased blood levels of unconjugated bilirubin
Increased urinary urobilinogen
Diagnostic clues to haemolytic anaemia x4
Increased reticulocyte count
Unconjugated bilirubinaemia and urinary urobilinogen
Abnormal appearance of red blood cells on film (spherocytes, sickle shaped or very hypochromic)
Increased red blood cell precursors in bone marrow
Incidence of hereditary spherocytosis
1 in 5000 live births in caucasians
Inheritance of hereditary spherocytosis
Usually autosomal dominant inheritance - BUT in 25% there is no family history and it is sporadic mutation
What is pathology of hereditary spherocytosis?
Mutation in gene for protein in red blood cell membrane - therefore RBC looses part of its membrane when it goes through the spleen
Therefore reduced surface-to-volume ratio and cell becomes spherical
Therefore less deformable than normal RBC and destruction of microvasculature of spleen
What are the clinical features of hereditary spherocytosis? x5
Clinical manifestations vary and patients can be completely asymptomatic or present during childhood or be intermittent - but can have:
- Jaundice
- Anaemia
- Mild-moderate splenomegaly
- Aplastic crisis with parvovirus B19
- Gallstones
Management of hereditary spherocytosis x2
Many have mild and therefore only require folic acid supplementation
Splenectomy is beneficial but only indicated if poor growth or troublesome symptoms - usually deferred until after 7 years old because of risk of sepsis
Management of aplastic crisis in hereditary spherocytosis
Usually requires 1 or 2 blood transfusions over 3-4 weeks whilst no red blood cells are produced
What is incidence of Glucose-6-phosphate dehydrogenase deficiency?
G6PD is commonest red cell enzymopathy - affects 100million people worldwide
10-20% of individuals from central africa, mediterranean and the middle east and far east
What is pathology of G6PD deficiency?
G6PD is an enzyme required to prevent oxidative damage to red cells - therefore red cells lacking the enzyme are susceptible to oxidant-induced haemolysis
Inheritance of G6PD deficiency?
It is x-linked therefore predominantly affects males. Heterozygous females are usually clinically normal and homozygous females (or one deletion + one mutation) will be affected
Clinical presentation of G6PD in children x2
1) Neonatal jaundice - onset in first 3 days of life - severe
2) Acute haemolysis precipitated by infection, certain drugs, fava beans (broad beans) and naphthalene (mothballs)
Details of haemolysis in G6PD - where does it occur and what does it cause x4
Mostly intravascular
Causes fever, malaise, passage of dark urine
Rapid fall in Hb
Diagnosis of G6PD
Between episodes almost all patients have a completely normal blood picture therefore diagnosis by looking at G6PD activity
During an episode G6PD may be misleadingly high due to increased reticulocyte production
Management of G6PD
Parents should be given advice about signs of acute haemolysis and provided with a list of what to avoid
Transfusions are rarely required even for acute episodes
When do B-thalassaemias present?
Delayed until after 6months of age when most of HbF (no B chains) has been replaced by HbA (with B chain)
Prevalence of sickle cell disease
1 in 2000 live births in UK
What does sickle cell disease encompass?
Sickle cell anaemia, sickle cell trait, HbSC disease and Sickle B-thalassaemia
What is HbSC disease?
One HbS and one HbC from other parent - HbC is point mutation in B-globin therefore also have no HbA
Features of sickle B-thalassaemia
Also have no normal B chains therefore no HbA and similar symptoms to sickle cell anaemia
Features of sickle cell trait?
About 40% HbS - do not have symptoms but are carriers and can pass on to children
Pathology of sickle
HbS polymerises forming stiff sickle shape with can get trapped in microcirculation - causing vaso-occlusion and therefore ischaemia
Exacerbated by low O2 tension, dehydration and cold
Clinical features of sickle x7
Anaemia (moderate 6-10g/dl) Infection Painful vaso-occlusive crises Acute anaemia (eg. in crises) Priapism Splenomegaly Long term problems
Types of infection risk in sickle
Infection from encapsulated organisms such as pnemococci and haemophilus influenzae
Increased osteomyelitis by salmonella
Due to hyposplenism and microinfarction in spleen in infancy
When is sepsis risk greatest in sickle
In early childhood - post-spleen destruction in infancy
Where is most commonly affected in painful crises of sickle x2
Bones of limbs and spines
Chest most serious as leads to hypoxia
What can cause acute anaemia in sickle? x3
Haemolytic crises (sometimes associated with infections) Aplastic crises (B19) Sequestration crises (sudden splenic or hepatic enlargement due to accumulation of sickled cells in spleen)