Paediatric haematology

Question 1

Site of haematopoiesis in the foetus varies

Answer 1

yolk sac up to 2 1/2 months, liver starts 1 months, spleen 2 1/2, bone marrow starts 4 1/2m and takes over until and beyond birth

Question 2

RBC’s at birth

Answer 2

• At birth, 55-65% is HbF - difference in red cell structure and metabolism
• Higher haematocrit (ratio of RBC volume to total blood volume - RBC sink to bottom)

Question 3

Haemoglobin switching

Answer 3

• Purpose = HbF has a higher oxygen affinity so binds O2 more strongly – able to take from mothers’ blood
• Chromosome 16 codes for zeta or alpha for the alpha chains
• Chromosome 11 codes for epsilon, gamma, beta or delta for the beta chains
• Can only activate alpha first then beta

Question 4

Child vs Adult – platelets

Answer 4

• Reach adult numbers by 18th week of gestation – normal prior to birth
• Platelets are initially large (larger platelet volume=important) but by birth they shrink to adult size
• Differences in function balance at birth

Question 5

Child vs Adult – WBC’s

Answer 5

• higher lymphocytes in children but actually don’t work as well = compensation
• IgG crosses the placenta
• IgA, IgD, IgE, IgG, IgM pass in breast milk
• Antibodies produced at 2-3 months – when vaccination happens
• Satisfactory immune response at 6 months

Question 6

Haemostasis at birth

Answer 6

• Present but imperfect
• Only fibrinogen, factors V, VIII, XIII levels are normal at birth
• Most haemostatic parameters reach adult values by 6 months

Question 7

Vitamin K

Answer 7

• II, VII, IX, X, protein C and protein S are vitamin K dependent
• Placental gradient means foetal vitamin K is 10% of mothers levels
  Exacerbation if on anti-convulsants – mother needs oral vitamin K
• Warfarin is teratogenic due to vitamin K depletion

Question 8

haemorrhagic disease of the new born Vitamin K cause

Answer 8

vit K factors too low in new born because mum is vit K deficient; treatment = give baby vit K injection

Question 9

Haemoglobinopathy

Answer 9

• Thalassaemia and sickle cell
• Issues with Hb switching, mutation on beta chain in sickle cell causing cells to sickle
• altered amounts of chains in thalassaemia; lots of alpha but reduced or absent beta chains – weird looking cells

Question 10

Congenital anaemias

Answer 10

• Bone marrow failure syndromes
• Bone marrow infiltration
• Haemoglobinopathy
• Peripheral destruction
• Blood loss

Question 11

Peripheral destruction

Answer 11

• Destruction of cell membrane
• Rh/ABO or other incompatibility
• Membrane defect – hereditary spherocytosis
• Enzyme defect – G6PD deficiency, Pyruvate Kinase deficient

Question 12

Blood loss

Answer 12

• Twin to twin transfusion – when one twin takes some of the other twins’ blood
• Feto-maternal haemorrhage in birth

Question 13

Acquired anaemias

Answer 13

• Nutritional deficiency – iron (common), B12, folate
• Bone marrow failure – normal stem cells but not making much blood
• Bone marrow infiltration e.g. malignancy – takes over bone marrow and space of haemopoiesis
• Peripheral destruction – haemolysis
• Blood loss

Question 14

Congenital Bleeding and bruising

Answer 14

• Platelet problem – decreased number or decreased receptors
• Clotting factor problem
• Connective tissue disorder

Question 15

Acquired Bleeding and bruising

Answer 15

• Trauma
• Tumour
• Infection – acute e.g. meningococcus or chronic e.g. HIV
• Immune disorder – primary (immune thrombocytopenia, TTP) or secondary (SLE)
• Bone marrow failure
• Drug related