Thalassaemia Flashcards
Define beta thalassaemia intermedia
Defined by RCOG as 7 or less transfusions per year or no transfusions per year
Define beta thalassaemia major
Homozygous beta thalassaemia trait - RCOG defines as more than 7 transfusions per year
Define haemoglobin H
3 alpha globin chains affected - haemoglobin consists of tetrameric beta and gamma chains - results in anaemia and splenomegaly
Define haemoglobin Barts
4 alpha globin chains affected - tetrameric gamma chains - incompatible to life - leads to fetal hydrops or early neonatal death (hb has a high affinity for oxygen)
Consequence of 1 defective alpha globin chain
Silent trait
Consequence of 2 defective alpha globin chains
alpha thalassaemia trait - mild anaemia
Consequence of beta thalassaemia major on pregnancy
Mild to moderate anaemia - folic acid 5mg recommended, iron replacement can be given if deficient, if symptomatic of anaemia, transfusion can be considered, risk of transmission to fetus
Pre-conception considerations of beta thal major and intermedia
Pituitary - hypogonadotrophic hypogonadism (ovulation induction with gonadotrophins, consider preimplantation genetic diagnosis)
Thyroid - low thyroid
Liver - iron, cirrhosis, gall stones
Pancreas - diabetes (test with fructosamine)
Heart - iron, cardiomegaly, heart failure, dysrhythmia
Blood - risk of VTE, infection risk (hep B/C), alloimmunisation
Infection - hepB/C, if splenectomy (risk of encapsulated infections)
Bone - osteoporosis
How is iron tissue deposition assessed in beta thal major and intermedia pre-conception
T2* cardiac MRI >20ms = low risk, <10ms high risk
T2* liver MRI or ferriscan - aim for 7mg/g dry weight pre conception, if >15mg/g high risk of cardiac iron - offer chelation 20-24 weeks
How is iron chelation managed pre-conception?
Aggressively.
Oral regimes should be stopped 3 month prior to conception (teratogenic)
IV desferrioxamine (short half life) can be used during ovulation induction
How often should beta thal intermedia and major be seen in pregnancy?
early scan 7-9 weeks, dating and anomaly scan, 4 weekly scans from 24 weeks
Monthly until 28 weeks then every 2 weeks in clinic
joint haem/mat med MDT involvement
Cardiac review at 28/40
What is the implication for beta thal major/intermedia on developing fetus?
Alloantibodies secondary to multiple transfusions = risk of fetal and neonatal haemolysis
Fetal growth restriction
What are the implications for beta thal major/intermedia on pregnant woman?
Co-morbidities - hypothyroid, diabetes
Cardiac decompensation and dysrhythmia in labour
Iron deposition as no longer using chelating agents
VTE risk
How should VTE risk be managed in beta thal major and intermedia?
Splenectomy or plt >600 = aspirin
Splenectomy AND plt >600 = aspirin and LMWH
Antenatal admission = LMWH
Postpartum LMWH
How should patients with beta thal major and intermedia be assessed for diabetes?
Hba1c is inaccurate - serum fructosamine should be used
Aim for <300 pre conception