Sickle Cell Anaemia Flashcards
Define Sickle Cell Anaemia
A chronic condition characterised by sickling of red blood cells, caused by inheritance of haemoglobin S (Hb S)
What is the difference between sickle cell anaemia, trait and disease
Sickle cell anaemia = Hb SS (homozygous)
Sickle cell trait = Hb AS (heterozygous)
Sickle cell disease = Anything involving sickling: compound heterozygosity for Hb S and C and HbS and beta-thalassaemia
Aetiology of Sickle Cell Anaemia
Autosomal recessive inheritance (point mutation on codon 6 of beta globin chain, polar -> non polar + insoluble -> HbS polymerises)
Red cell becomes distorted, dehydrated and adhered to vascular endothelium
Sickling precipitated by infection, dehydration, hypoxia and acidosis
Symptoms due to shortened RBC lifespan -> haemolysis -> vessel occlusion
Epidemiology of Sickle Cell Anaemia
Rarely presents before 4-6 months
Distribution matches that of endemic plasmodium falciparum malaria
Common in Africa, Caribbean, Middle East
Symptoms of Sickle Cell Anaemia
Early manifestations:
1. Dactylitis (pain in bones) in the small bones of hands and feet 2. Splenic sequestration 3. Infection e.g. S. pneumoniae
Anaemia: fatigue, SOB Recurrent infection (autosplenectomy) Chronic/recurrent leg ulcers RUQ pain (gallstones) Chronic hip or shoulder pain (avascular necrosis) Myalgia and arthralgai Fits or stroke Visual loss (Proliferative retinopathy)
Fever, cough, chest pain, tachypnoea (acute chest syndrome)
Present erection/priapsim and impotence (corpora cavernosa)
Signs of Sickle Cell Anaemia on examination
Anaemia: pallor
Vaso-occlusive crises: Joint or muscle tenderness of swelling (avascular necrosis) | Short digits (infarction in small bones) | Cotton wool spots on the retina
Splenomegaly in early disease (sequestration crisis) -> will shrink as the patient gets older
Priapism
Dactylitis
Osteomyelitis
Aplastic crisis signs (parvovirus B19)
What classes as a sickle cell emergency
Septic shock (BP <90/60) Neurological signs or symptoms SpO2 <92% on air Symptoms/signs of anaemia with Hb <5 or fall >3g/dl from baseline Priapism >4 hours
Investigations for Sickle Cell Anaemia
FBC: anaemia (6-9g/dL), high reticulocytes (not in aplastic crisis)
Blood film: sickle cells, boat cells, target cells + Howell Jolly bodies (hyposplenism)
Solubility testing: solution becomes turgid
Electrophoresis: HbS present, Increased HbF levels
High performance liquid chromatography: HbF predominant in infants, no HbA
X-ray Hip: Infarctions seen by irregular margins or moth-eaten destruction with overlying periosteal new bone formation (avascular necrosis)
MRI/CT head: if neuro symptoms
CXR: Acute chest syndrome
Management for Sickle Cell
Conservative: trigger avoidance | good hygiene and nutrition | genetic counselling | prenatal screening | monitor spleen | pregnancy care
Medical:
Vaccination
Hydroxyurea (increases HbF levels)
Folic acid
Prophylactic antibiotics - penicillin, vacciantion
Individual analgesia protocol (opioids, paracetamol, NSAIDs, pregabalin/gabapentin)
Chest syndrome stroke, acute events: Blood transfusion
Surgical: Bone marrow transplants | Joint replacement for avascular necrosis
Management for sickle cell crises
Oxygen if hypoxic
Pain relief (opioids, most commonly diamorphine), oral opioids for children
Hydration - IV fluids or oral depending on severity
Keep warm
Antihistamine
Exclude infection: Blood and urine cultures, CXR, Give antibiotics
Management for sickle cell acute chest syndrome
Oxygen + incentive spirometry
Analgesia - paracetamol or ibuprofen or ketorolac etc.
Broad-spectrum antibiotics
Antihistamine - diphenhydramine, given as opioids cause pruritus
Blood transfusion
Hydration
What are the indications for Haematopoietic stem cell transplantation
- CNS disease
- Recurrent severe vaso-occlusive crisis
- Recurrent acute chest syndrome if hydroxyurea fails
Complications of sickle cell anaemia
Lungs: acute chest syndrome, chronic damage, pulmonary HTN
Urinary tract: haematuria, impaired concentration, renal failure, priapism
Brain: stroke, cognitive impairment
Eyes: proliferative retinopathy
Sequestration crisis -> splenectomy
Chronic cholecystitis -> cholecystectomy
Prognosis for Sickle Cell Disease
Chronic organ damage due to sickle cell results in many medical complications, although some prophylactic treatments can reduce incidence
Without bone marrow transplant, median age of death is 42 years for men and 48 years for women with HbSS
50% of children with sickle cell die before their first birthday
Morbidity and mortality declining
