Paediatric Haematology Flashcards
What are the 4 main things to remember when treating a child as opposed to an adult?
1) May weigh more or less than 70kg
2) Congenital conditions are more relevant
3) Everything is moving
4) Children exist within a family - management often involved siblings, parents etc.
What are the 6 differences between child and adults RBCs?
1) Child site of haematopoiesis varies
2) Hb switching occurs
3) At birth 55-65% of Hb is HbF
4) Difference in red cell structure and metabolism
5) Larger red blood cells in children
6) Children have a higher haematocrit
What are the sites of haematopoiesis in children?
In embryo - yolk sac then liver and spleen
Bone marrow takes over but if this is insufficient liver and spleen can be re-recruited to help
What is Hb switching?
Chr 16 can produced zeta or alpha chains
Chr 11 can produce epslon, gamma, beta and delta chains
Different types of Hb composed of different chain combos are produced at different periods of gestation
What different Hbs are produced between 4-14 weeks of gestation due to Hb switching?
Hb Gower-1 = 2 zeta, 2 epslon
Hb Portland = 2 zeta, 2 gamma
Hb Gower-2 = 2 alpha, 2 epslon
What type of Hb is produced >14 weeks of gestation til birth due to Hb switching?
HbF = alpha 2 gamma 2
What 2 types of Hb are produced in the neonatal stage?
HbA = alpha 2 beta 2
HbA 2 = alpha 2 delta 2
How do child WBC counts differ to adult?
Similar numbers but children have higher lymphocyte counts
What type of Ig can cross the placenta, why is this physiologically appropriate?
IgG (IgM cannot)
IgG confers wider protection, whereas IgM would only confer protection against stuff you were currently exposed to
What is an important source of passive immunity in neonates?
Breast milk - has IgA, IgD, IgE, IgG, IgM
At how many months do children start producing there own Ab?
2-3 months
After how many months can children mount a satisfactory immune response?
6 months
At how many months are immunisations given?
2 months, with boosters
Although child cannot mount a satisfactory immune response at this point without vaccination until 6 months there would be a lot of neonatal deaths, vaccination at 2 months provides just enough protection
Which type of blood cell reaches adult levels first and why?
Platelets - reach adult leaves by week 18 of gestation
Birth is a bloody process, coagulation is very important
In what 3 ways do platelets at birth differ to adult platelets?
1) Initially larger but by birth slim down to adult size
Functionally different at birth:
2) Hyporesponsive to certain agonists
3) Hyperresponsive to vWF
For what 3 reasons is haemostasis although present at birth not perfect?
1) Coagulation proteins do not cross the placenta effectively
2) Only fibrinogen, FV, FVIII and FXIII are normal at birth
3) Most haemostatic parameters reach adult values by 6 months
Few bleeding problems are seen clinically despite imperfect haemostasis, in which 2 situations may they occur?
1) Pre term babies
2) Ill babies
Which 6 coagulation factors are Vit K dependent?
1) FII (thrombin)
2) FVII
3) FIX
4) FX
5) Protein C
6) Protein S
Why are neonates Vit K deficient and thus require IM vit K?
Because the placental gradient means fetal Vit K in 10% of mother
What condition is prevented by routine neonatal Vit K?
Haemorrhagic disease of the newborn
Why should warfarin be avoided in pregnancy?
Its teratogenic
In what situation is Vit K deficiency of the newborn exacerbated and therefore mother requires oral Vit K?
If mother is on anti convulsants
What are the 5 key things about neonatal haemostasis?
1) Pro-coagulant factors reduced, 2,7, 9,,11,12, pre kallikrein, high molecular weight kininogens
2) Reduced concentration of coagulation inhibitors: ATIII, heparin co factor 2, TFPI, Protein C, Protein S
3) Unique forms of fibrinogen and plasminogen
4) Raised D dimers and vWF
5) Platelet aggregation differs
What are the 5 congenital causes of anaemia in childhood?
1) Hb synthesis problem: haemoglobinopathy (sickle cell of thalassemia)
2) Bone marrow failure syndromes
3) Bone marrow infiltration
4) Peripheral destruction - making RBCs but they are being destroyed
5) Blood loss
Give the 4 causes of peripheral destruction of RBCs leading to anaemia in childhood?
1) Rh/ABO or other incompatibility
2) Membrane defect: hereditary spherocytosis
3) Enzyme defect: G6PD deficiency, PK deficiency
4) Infection
Why is peripheral destruction of RBCs particularly relevant in new born?
Haematopoesis stops for about 10 weeks post birth - RBCs that are being destroyed are not replaced
ABO incompatibility is more common than Rh incompatibility, why does Rh cause more problems clinically?
Mother ABO IgM cannot cross the placenta
Childs ABO Ag not presented on RBCs til after birth
Give 2 causes of blood loss leading to congenital anemia?
1) Twin to twin transfusion: can be shocking, one twin large and red, the other small and white
2) Fetomaternal haemorrhage
What is the main cause of acquired childhood anaemia?
Iron deficiency
Give the 5 causes of acquired childhood anaemia?
1) Nutritional deficiency: iron, B12, folate
2) Bone marrow failure
3) Bone marrow infiltration
4) Peripheral destruction: haemolysis
5) Blood loss
What are the 3 congenital causes of bleeding and bruising in the neonate?
1) Platelet problem
2) clotting factor problem
3) Connective tissue disorder
What are the 6 acquired causes of bleeding and bruising in the neonate?
1) Trauma: both accidental and non accidental
2) Tumour
3) Infection: acute eg. meningococcus, chronic eg. HIV
4) Immune disorder: primary - immune thrombocytopenia, TTP, secondary SLE and ALPS
5) Bone marrow failure
6) Drug related
