Anaemia - Sickle Cell (Normocytic) Flashcards
Epidemiology
Africa
India
Middle East
Family History
Definition
Autosomal recessive haemoglobinopathy affecting beta globin chains resulting in vaso-occlusive crisis + hemolytic anemia
= Anti-malarial properties as a carrier ( falciparum malaria)
= Upper resp tract infections is the most common cause of death in adults with sickle cell
Aetiology
Amino acid substitution on the gene coding for the beta globin gene (Glu [GAG] -> Val [GTG] on position 6) = chromosome 11 = Hbs production instead of HbA = Irreversible RBC sickling
Heterozygous state
[HbAS]
Sickle cell trait = Carriers
No disability
Still protective against p.falciparum
Still may experience symptoms in hypoxia (unpressurised aircraft, anesthesia)
Homozygous state
[HbSS] - HbA2 and HbF production unaffected
Sickle cell anaemia -> Sufferers
Since the synthesis of HbF is normal, the disease doesn’t manifest itself until HbF decreases to adult levels (~ 6 months age)
Sickling = precipitated by infection, dehydration, cold, acidosis, or hypoxia
Pathophysiology
HbS polymerases when deoxygenated causing RBCs to deform producing sickling cells = fragile and haemolyse = decreased saturation + block small blood vessels.
- Initially they can return to normal shape once oxygenated but with repeated sickling lose membrane flexibility + stay sickled = dehydrated + dense
LESS EFFECIENT
RISK OF SEQUESTRATION
DIE QUICKER
Intra + extravascular hemolysis
Signs
HbS releases O2 more readily than normal RBCs so patients may feel well despite being anemic
General anemia +PREHEPATIC JAUNDICE (hemolytic anemia)
Dactylitis = swelling of fingers or toes which give it sausage shape appearance (due to vaso-occlusions)
Avascular necrosis
Osteomyelitis: mc due to salmonella
Acute chest syndrome: dyspnoea, chest pain, hypoxia, pulmonary infiltrates on X ray
Stroke
Hematuria + Proteinuria
PRIAPISM = Blood trapped in penis = painful prolonged erection = needs aspiration
Types of crisis:
- sequestration crisis = abdo pain, splenomegaly, hypovolaemic shock
- aplastic crisis = parvovirus 19 causes bone marrow suppression = fatigue, anaemia, pallor, NO splenomegaly
- haemolytic crisis = increased rate of intravascular and extra vascular haemolysis
- Intravasc haemolysis - marked by increased HAPTOGLOBIN
- Extravasc haemolysis = autosplenectomy = risk of infection from encapsulated bacteria
Diagnosis
New born screening (Guthrie heel prick test)
- tests for sickle cell, hypothyroidism, CF
First line = FBC + blood film
- NORMOCHROMIC NORMOCYTIC with increased reticulocytes
- Sickled RBC + Howell Jolly Bodies
- low Hb
GOLD STANDARD = Hb electrophoresis = proportions of Hb (90% HbS)
Treatment
Acute complicated crisis:
- IV fluid + analgesia (NSAIDS) + O2 (+ Abx if infection)
Long term:
- Avoid precipitants
- Drugs = HYDROXYCARBAMIDE
-> increases amount of HbF
-> Side effect = neutropenia
-> Alternative = L-GLUTAMINE
+ folic acid supplements
- Transfusion + Fe chelation
GOLD STANDARD = BM stem cell transplant
Complications
Precipitated by infection, cold, hypoxia (acidosis), dehydration:
Splenic sequestration - can cause autosplenectomy
Vaso-occlusive crises - sickle cell polymerizes + trap in long bone BVs
- CNS blood vessels blockage = stroke = USS to see risk of impending stroke, blood transfusions can prevent by reducing HbS
- Acute chest syndrome/crisis = pul vessel vaso-occlusion + cause resp distress = EMERGANCY
- Mesenteric ischemia
- Avascular necrosis of femoral head, leg ulcers
Aplastic crisis - temporary loss of creation of RBC -> triggered by parvovirus B19
Osteomyelitis = common in sickle cell
- usually due to s.aureus but in those patients = SALMONELLA
More susceptible to encapsulated bacteria:
Strep pneumoniae
H. influenzae
Neisseria meningitidis
Salmonella -> osteomyelitis
PROPHYLAXIS = Penicillin V in children = phenoxymethylpenicillin
Pneumococcal vaccines
