Anaemia (SCA) Flashcards
Describe the pathophysiology of SCA [+]
- SINGLE-BASE MUTATION of
- ADENINE to THYMINE which produces a substitution of VALINE for
- GLUTAMIC ACID at the SIXTH CODON of the beta-globin chain
- In the heterozygous state (sickle cell trait), only one chromosome carries the
- gene - these are carriers of the disease
- In the homozygous state (SICKLE CELL ANAEMIA), both genes are abnormal
- Sickle cell haemoglobin (HbS) is insoluble and polymerises when deoxygenated
- The flexibility of the cells is decreased and they become rigid and take up their characteristic sickle appearance
- This process is initially reversible but, with repeated sickling, the cells eventually lose their membrane flexibility and become IRREVERSIBLY SICKLED
- This causes a shortened RBC survival resulting in haemolysis
- Impaired passage of cells through the microcirculation, leading to obstruction of small vessels and tissue infarction and thus intense pain
Describe the relationship between SCA and malaria [1]
Having one copy of the gene (sickle cell trait) reduces the severity of malaria.
As a result, patients with sickle cell trait are more likely to survive malaria and pass on their genes.
State 4 acute clinical presentations of SCA [6]
- Vaso-occlusive crises
- Acute chest syndrome
- Pulmonary hypertension
- Anaemia
- Priapism
- Splenic sequestration crisis
Describe the clinical presentation of a vaso-occlusive crisis in SCA [3]
(Which bones are more commonly impacted?)
Vaso-occlusive crises:
- Acute pain in the hand and feet (dactylitis) owing to vasoocclusion of the small vessels and avascular necrosis of the bone
marrow in children
- Possible to have CNS infarction in children leading to stroke,
seizures and cognitive defects
- In adults there is pain in the long bones such as the femur, spine, ribs and pelvis due to avascular necrosis of the bone marrow
A vaso-occlusive crisis is typically associated with what other clinical presentation? [1]
fever
What pathology can a vaso-occlusive crisis lead to in men? [1]
priapism: trapping blood in the penis, causing a painful and persistent erection
Describe the clinical presentation of acute chest syndrome in SCA [5]
What can cause this? [3]
A vaso-occlusive crisis of the pulmonary vasculature: presents with
- Fever
- SOB
- Chest pain
- Cough
- Hypoxia
Caused by infection (due to Chlamydia, mycoplasma and
Streptococcus pneumoniae), fat embolism from necrotic bone
marrow or pulmonary infarction due to sequestration of sickle
cells (where sickle cells get trapped in the pulmonary vasculature)
How does an acute chest syndrome present on CXR? [1]
Pulmonary infiltrates
Describe the management for an acute chest syndrome presentation [6]
1st line:
- Oxygen & Incentive spirometry using a machine that encourages effective and deep breathing, prevents atelectasis
Plus:
- Analgesia
Plus:
- broad-spectrum antibiotics (because bacterial pneumonia cannot always be ruled out)
Consider:
- Antihistamine (many opioids cause pruritus, which should be managed with an oral antihistamine)
Consider:
- Blood transfusion
Consider:
- Hydration
BMJ BP
Describe the management for an vaso-occlusive crisis presentation [6]
1st line:
- Analgesia
Plus:
- Supportive care
Plus:
- broad-spectrum antibiotics
Consider:
- Antihistamine
Consider:
- Blood transfusion
Consider:
- Hydration
Define what is meant by pulmonary hypertension [1]
Why does SCA lead to PH? [1]
Defines as a mean pulmonary artery pressure greater then
25mmHg by right heart catheterisation
caused by damage from repeated chest crises and
repeated thromboembolism and intravascular haemolysis
Describe what is meant by aplastic crisis in SCA [1]
This often occurs after infection of which organism? [1]
Temporary absence of the creation of new red blood cells
. It is usually triggered by infection with parvovirus B19.
Describe what is meant by a splenic sequestration crisis in SCA [1]
Splenic sequestration crisis:
- The rapid pooling of blood in the spleen due to sickled cells block the blood vessels leading out of the spleen - splenomegaly, hypovolemic shock, and potentially death if not promptly treated.
- This event is more common in paediatric patients.
State 9 chronic complications of SCA [9]
- Anaemia
- Infections
- Leg ulcers
- Ocular complications
- Skeletal complications
- Renal complications
- Cardiopulmonary complications
- Neurological complications
- Growth retardation and delayed puberty
Describe the following chronic complications of SCA [4]
- Anaemia
- Infections
- Leg ulcers
- Growth retardation and delayed puberty
Anaemia:
- chronic haemolytic anaemia is a constant feature in sickle-cell patients, characterized by pallor, fatigue, and exertional dyspnoea.
Infections:
- Functional asplenia due to recurrent splenic infarctions increases susceptibility to encapsulated bacterial infections, such as Streptococcus pneumoniae and Haemophilus influenzae.
Leg ulcers:
- Chronic venous insufficiency resulting from vaso-occlusion can lead to non-healing leg ulcers, predominantly around the medial malleoli.
Growth retardation and delayed puberty:
- due to chronic hypoxia and undernutrition related to increased metabolic demands from their condition.
According to NICE guidelines, which laboratory test is considered the gold standard for confirming the diagnosis of sickle cell anemia?
a) Complete Blood Count (CBC)
b) Hemoglobin Electrophoresis
c) Serum Ferritin
d) Coagulation Profile
According to NICE guidelines, which laboratory test is considered the gold standard for confirming the diagnosis of sickle cell anemia?
a) Complete Blood Count (CBC)
b) Hemoglobin Electrophoresis
c) Serum Ferritin
d) Coagulation Profile
