Haemoglobinopathies Flashcards
(27 cards)
When does homozygous sickle cell anaemia (HbSS) first present?
Usually in early childhood with anaemia + jaundice due to chronic haemolytic anaemia
Painful hands + feet w/ inflammation of fingers due to dactylitis
What are precipitants of having a chest crisis?
Dehydration
Infection (eg. sore throat)
Cold or damp conditions
Unaccustomed exercise
Stress
Pregnancy
Operations
What is the management of a chest crisis?
- hosp admission
- IV fluids, oxygen, adequate analgesia
- infection should be treated w/ antibiotics
- definitive investigation is haemoglobin electrophoresis which will demonstrate HbS, absent HbA, and variable HbF level
- exchange transfusion may be needed to reduce level of his sickle cells to less than 30%
- may benefit from long-term hydroxyurea which raises the HbF level + reduces number of crises
What are haemoglobinopathies?
- caused by an abnormality in globin chain structure
- caused by single gene disorders
- most common = sickle cell diseases
- there are others eg. congenital dyserythropoietic anaemia (CDA)
What are thalassaemias?
Absent or reduced alpha or beta globin chains which form the normal adult HbA (a2b2)
Caused by mutations in regulatory genes
Might overlap with haemoglobinopathies: HbS/beta-thalassaemia
Genetics of sickle cell disease
Point mutation in the beta globin gene on chromosome 11
Amino acid substitution (adenine to thymine)
Causes glutamic acid being substituted by valine at position 6
Different mutations in beta globin chain structure lead to diff types of haemoglobin eg. HbD, HbC, HbE
How do you take a sickle history?
What are the chains and genes in normal haemoglobin?
Normal haemoglobin (HbA) consists of 2 alpha and 2 beta chains
This is made from 2 alpha and 4 beta globin genes
What are the main categories of sickle cell disease?
- Homozygous sickle cell anaemia:
Inherit the abnormal sickle gene from both parents so phenotype is HbSS
- Heterozygous mutation (sickle cell disease):
Inherit two different recessive alleles one of the sickle gene and the other another haemoglobin variant of the beta globin gene - Sickle-thalassaemia:
Inherit a sickle gene and a thalassaemia gene causing abnormal production and structure - severity depends on which thalassaemia gene is inherited
Sickle cell trait:
Inherits a single sickle copy and rarely causes symptoms (a carrier)
Inheritance pattern of sickle cell disease
Autosomal recessive
How is sickle cell diagnosed?
Blood results in sickle cell
Examples of acute sickle cell crises
Vaso-occlusion
Acute chest syndrome
Aplastic crisis
Hand foot syndrome
What is vaso-occlusive crisis?
Symptoms and findings in an acute chest crisis
Management of acute chest syndrome
Exchange transfusion
What is an aplastic crisis?
What is hand-foot syndrome?
Complciartions of sickle cell disease
Jaundice
Dactylitis
Chronic organ damage
Retinopathy
Pulmonary HTN
Priapism
Stroke
Avascular necrosis
Sequestration
Sepsis
Increased susceptibility to encapsulated bacteria
Ongoing management for sickle cell disease
Indications for hydroxyurea in sickle cell disease
More than 3 acute painful episodes needing admission
Acute chest syndrome needing transfusion/HDU
Previous stroke
Which bacterial infections are sickle cell patients more susceptible to?
Encapsulated such as H.influenzae and Strep pneumoniae due to hyposplenism
What is alpha thalassaemia?
What is beta thalassaemia?
A thalassaemia leading to reduced/absent production of the beta globin chains
