thalassaemias

v.djabatey
Mind Map by v.djabatey, updated more than 1 year ago
v.djabatey
Created by v.djabatey about 6 years ago
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Paediatrics (Haematological disorders) Mind Map on thalassaemias, created by v.djabatey on 03/18/2014.

Resource summary

thalassaemias
1 beta-thal
1.1 most often occur in people from
1.1.1 Indian subcontinent
1.1.2 Mediterranean
1.1.3 Middle East
1.2 2 types- both have severe reductn in prodn beta-globin (& so drop in HbA prodn)
1.2.1 disease severity depends on amount of residual HbA & HbF prodn
1.2.1.1 beta-thal major
1.2.1.1.1 MOST SEVERE FORM
1.2.1.1.2 can't make HbA (alpha2 beta 2) cos of abnormal beta-globin gene
1.2.1.1.3 clinical features
1.2.1.1.3.1 pallor
1.2.1.1.3.2 jaundice
1.2.1.1.3.3 bossing of skull & maxillary overgrowth
1.2.1.1.3.4 hepatosplenomegaly
1.2.1.1.3.5 need for repeated blood transfusions
1.2.1.2 beta-thal intermedia
1.2.1.2.1 milder form & variable severity
1.2.1.2.2 beta-globin mutations allow small amount of HbA &/or large amount of HbF to be made
1.3 clinical features
1.3.1 severe anaemia
1.3.1.1 transfusion-dependent
1.3.1.2 from age 3-6 months old
1.3.1.3 + jaundice
1.3.2 failure to thrive/growth failure
1.3.3 extramedullary haemopoiesis
1.3.3.1 prevent by regular blood transfusions
1.3.3.1.1 if not prevented ->
1.3.3.1.1.1 hepatosplenomegaly
1.3.3.1.1.2 bone marrow expansion
1.3.3.1.1.2.1 -> classical facies
1.3.3.1.1.2.1.1 maxillary overgrowth & skull bossing
1.3.3.1.1.2.1.1.1 rare in developed countries
1.4 Mx
1.4.1 lifelong monthly RBC transfusions
1.4.1.1 beta thal fatal w/o these
1.4.1.2 aim= keep [Hb] > 10g/dl
1.4.1.2.1 to reduce growth failure
1.4.1.2.2 to prevent bone deformation
1.4.1.3 cause chronic Fe overload (cos repeated)
1.4.1.3.1 ->cardiac failure
1.4.1.3.2 ->liver cirrhosis
1.4.1.3.3 ->diabetes
1.4.1.3.4 ->infertility
1.4.1.3.5 ->growth failure
1.4.1.3.6 so Rx w/ ... from 2-3 years old
1.4.1.3.6.1 iron chelation e.g. subcut desferrioxamine
1.4.1.3.6.2 oral iron chelator drug e.g. deferasirox
1.4.1.3.6.3 compliance hard but good comp w/ both -> 90% chance of living til 40s
1.4.1.3.6.3.1 if can't comply, high mortality in early adulthood from overload
1.4.1.4 complications of multiple transfusions
1.4.1.4.1 iron deposition
1.4.1.4.1.1 the most imp complication
1.4.1.4.1.1.1 seen in all pts
1.4.1.4.1.2 heart-cardiomyopathy
1.4.1.4.1.3 liver-cirrhosis
1.4.1.4.1.4 pancreas- diabetes
1.4.1.4.1.5 pituitary gland- delayed growth & sexual maturation
1.4.1.4.1.6 skin-hyperpigmentation
1.4.1.4.2 antibody formation (10% of kids)
1.4.1.4.2.1 allo-antibodies to transfused RBCs in pts make finding compatible blood hard
1.4.1.4.3 infection (now uncommon <10% of kids)
1.4.1.4.3.1 hepatitis A, B, C
1.4.1.4.3.2 HIV
1.4.1.4.3.3 malaria
1.4.1.4.3.4 prions e.g. new variant CJD
1.4.1.4.4 venous access
1.4.1.4.4.1 common prob
1.4.1.4.4.2 often traumatic in young kids
1.4.1.4.4.3 may need central venous access device e.g. portacath
1.4.1.4.4.3.1 predispose to infection
1.4.2 bone marrow transplantation
1.4.2.1 the only cure
1.4.2.2 only for kids w/ an HLA-identical sibling
1.4.2.2.1 cos then 90-95% chance of transfusion independence & long-term cure (success) but 5% chance of transplant-related mortality
1.5 prenatal diag
1.5.1 for parents both heterozyg for beta-thal
1.5.1.1 means 1 in 4 risk of having an affected child
1.5.2 offer DNA analysis of chorionic villus sample + genetic counselling
1.5.2.1 help parents make informed decision re to continue preg
2 beta-thal trait
2.1 heterozygotes usually asymptomatic
2.2 hypochromic & microcytic RBCs
2.2.1 so can be confused w/ mild iron def
2.2.1.1 tell apart by measuring serum ferritin
2.2.1.1.1 low in iron def NOT beta thal trait
2.2.1.1.1.1 measure serum ferritin in pts w/ mild anaemia & microcytosis before starting iron supplements
2.2.1.1.1.1.1 avoid unnecessary Fe therapy
2.3 mild or absent anaemia
2.3.1 + disprop drop in MCH (18-22 fl) & MCV (60-70 fl)
2.3.1.1 so RBC count usually raised (> 5.5 x 10^12/L)
2.4 raised HbA2= most imp diag feature
2.4.1 usually seen in about 5%
2.5 mild elevatn of HbF by 1-3% in 50%
3 alpha-thal
3.1 manifestation depends on no of functional alpha-globin genes
3.1.1 alpha-thal major
3.1.1.1 aka Hb Barts hydrops fetalis
3.1.1.2 cause= deletion of all 4 alpha globin genes
3.1.1.2.1 so no HbA (alpha2 beta2) can be made
3.1.1.3 occurs in families of S. East Asian origin
3.1.1.4 presents mid-trimester
3.1.1.4.1 fetal hydrops (oedema & ascites)
3.1.1.4.1.1 from fetal anaemia
3.1.1.4.1.2 always fatal in utero or within hours of delivery
3.1.1.4.1.2.1 long-term survivors are those who got monthly intrauterine transfusion til delivery + lifelong monthly transfusions after birth
3.1.1.5 diag
3.1.1.5.1 Hb electrophoresis
3.1.1.5.2 Hb HPLC (high performance liquid chromatography)
3.1.1.5.2.1 only shows Hb Barts
3.1.2 HbH disease
3.1.2.1 3 of alpha-globin genes deleted
3.1.2.2 px often = mild-moderate anaemia
3.1.2.3 some pts transfusion-dependent
3.1.3 healthy ppl have 4 func alpha-globin genes
3.1.4 alpha-thal trait
3.1.4.1 = deletion of 1 or 2 alpha-globin genes
3.1.4.2 asymptomatic
3.1.4.3 mild/absent anaemia
3.1.4.4 hypochromic & microcytic RBCs
3.1.4.4.1 so can be confused w/ iron def
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