Sickle Cell Summary

Genetics & Types

  • Hb SS: Sickle cell anemia (most severe)
  • Hb AS: Sickle cell trait (usually asymptomatic)
  • Autosomal recessive inheritance
  • Malaria protection hypothesis

Acute Complications

  • Vaso-occlusive crisis (pain crisis)
  • Acute chest syndrome
  • Splenic sequestration
  • Stroke
  • Priapism
  • Infections

Chronic Complications

  • Chronic anemia
  • Avascular necrosis
  • Renal failure
  • Pulmonary hypertension
  • Leg ulcers
  • Retinopathy

Acute Management

  • Aggressive pain control
  • Hydration
  • Oxygen if hypoxic
  • Antibiotics for fever
  • Transfusion if indicated

Preventive Care

  • Penicillin prophylaxis
  • Vaccinations
  • Hydroxyurea therapy
  • Avoiding triggers
  • Regular monitoring

Diagnostic Tests

  • Hemoglobin electrophoresis
  • Peripheral blood smear
  • Reticulocyte count
  • LFTs, renal function
  • Transcranial Doppler

Curative Options

  • Bone marrow transplant
  • Gene therapy (emerging)
  • Limited by donor availability
  • 10% mortality in children

Sickle Cell Disease

Inherited hemoglobin disorder causing chronic hemolytic anemia and vaso-occlusive complications

Epidemiology & Genetics

Sickle cell disease is estimated to affect 1 in every 2000 live births in England, and it is now the most common genetic condition at birth.

Geographic Distribution

  • Highest prevalence: Black African and Caribbean
  • Also common in: Middle East, India, Mediterranean
  • South and Central America
  • Common factor: History of malaria exposure

Genetic Inheritance

  • Hb SS: Sickle cell anemia (homozygous)
  • Hb AS: Sickle cell trait (carrier)
  • Autosomal recessive pattern
  • 25% risk if both parents carriers

Pathophysiology

Sickle hemoglobin has an abnormal beta-globin chain that causes it to polymerize when deoxygenated, which distorts the erythrocyte into a sickle shape.

Sickling Process

Molecular Mechanism

  • HbS polymerization when deoxygenated
  • RBC deformation into sickle shape
  • Increased rigidity and fragility
  • Shortened RBC lifespan (16-20 days)

Clinical Consequences

  • Vaso-occlusion → tissue ischemia
  • Hemolytic anemia
  • End-organ damage
  • Increased infection risk

Sickling Triggers

Common precipitating factors for sickling:

  • Intercurrent illness
  • Psychological stress
  • Cold temperatures
  • Pregnancy
  • Dehydration
  • Hypoxia (exertion, anesthesia, high altitude)

Acute Complications

Vaso-occlusive Crisis

  • Most common complication
  • Bone pain (back, limbs)
  • Local warmth, tenderness, swelling
  • Fever may be present

Acute Chest Syndrome

  • Chest pain, tachypnea, cough
  • Fever + new CXR infiltrate
  • Can progress to ARDS
  • Causes: Infection, infarction, fat embolism

Acute Anemia Causes

  • Splenic sequestration (children)
  • Transient red cell aplasia (parvovirus B19)
  • Hepatic sequestration
  • Severe hematuria

Infectious Complications

  • Pneumococcal sepsis
  • Gram-negative sepsis
  • Osteomyelitis (Salmonella, Staph)
  • UTIs, respiratory infections

Other Acute Complications

Complication Clinical Features
Priapism Painful erection, affects 89% of males by adulthood
Stroke Ischemic in children, hemorrhagic in adults
Renal Impairment Papillary necrosis, hematuria, acute renal failure
Hepatic Crisis Right upper quadrant pain, hepatomegaly

Chronic Complications

Musculoskeletal

  • Avascular necrosis (hip, shoulder)
  • Chronic arthritis
  • Vertebral collapse
  • Osteopenia

Cardiopulmonary

  • Pulmonary hypertension (33% of adults)
  • Chronic sickle lung
  • Heart failure
  • Restrictive lung disease

Renal & Hepatic

  • Chronic kidney disease
  • Proteinuria, hematuria
  • Gallstones (chronic hemolysis)
  • Hepatic dysfunction

Neurological & Ocular

  • Silent cerebral infarcts (17% children)
  • Cognitive impairment
  • Epilepsy (10-15% patients)
  • Proliferative retinopathy

Other Chronic Issues

  • Leg ulcers: Painful, near ankles, bilateral
  • Growth impairment: Delayed puberty (2-3 years)
  • Nutritional deficiencies: Increased metabolic demands
  • Erectile dysfunction: From recurrent priapism

Diagnosis

When to Suspect SCD

Suspect sickle cell disease in high-risk groups with:

  • Child 9-18 months with dactylitis (hand/foot swelling)
  • Sudden severe infection
  • Features of acute crisis
  • Chronic complications suggestive of SCD

Diagnostic Tests

Test Findings
Hemoglobin electrophoresis Gold standard for diagnosis
Peripheral blood smear Sickled cells, target cells, Howell-Jolly bodies
Complete blood count Anemia (Hb 6-8 g/dL), elevated reticulocytes
Solubility test (Sickledex) Screening test, cannot distinguish trait from disease

Confirmatory testing: Always requires both initial and confirmatory positive tests for diagnosis.

Management

Curative option: Bone marrow transplantation is the only cure but has 10% mortality in children and limited by donor availability.

Preventive Management

Childhood Prevention

  • Early diagnosis (newborn screening)
  • Pneumococcal immunization
  • Penicillin prophylaxis (<5 years)
  • Nutritional counseling
  • Prompt infection treatment

Chronic Disease Management

  • Hydroxycarbamide (hydroxyurea)
  • L-glutamine, crizanlizumab
  • Voxelotor
  • Chronic transfusion therapy
  • Genetic counseling

Acute Crisis Management

Vaso-occlusive Crisis Treatment
  1. Comprehensive pain assessment
  2. Aggressive analgesia: Paracetamol, NSAIDs, opioids
  3. Oxygen therapy if hypoxic
  4. Fluid replacement (hydration)
  5. Antibiotics if infection suspected
  6. Blood transfusion if severe anemia

Acute Chest Syndrome Management

Emergency Protocol
  1. Oxygen therapy to maintain saturation >95%
  2. Blood transfusion (simple or exchange)
  3. Broad-spectrum antibiotics
  4. Analgesia (avoid respiratory depression)
  5. Fluid management (careful balance)
  6. Bronchodilators if bronchospasm

Trigger Avoidance

Patient education to avoid:

  • Dehydration
  • Cold exposure
  • High altitudes
  • Strenuous exercise
  • Extreme temperatures
  • Stress

Monitoring & Follow-up

Regular Assessments

  • Growth and development (children)
  • Transcranial Doppler (stroke risk)
  • Echocardiogram (pulmonary hypertension)
  • Renal function monitoring
  • Ophthalmology screening

Complication Screening

  • Silent cerebral infarcts (MRI)
  • Avascular necrosis (X-ray/MRI)
  • Pulmonary function tests
  • Iron overload (ferritin, MRI)

Multidisciplinary care involving hematologists, primary care, pain specialists, psychologists, and social workers is essential for comprehensive sickle cell disease management.