Sickle Cell Disease is a hereditary hemoglobinopathy caused by a mutation in the β-globin gene, resulting in the production of abnormal hemoglobin S (HbS). Under low oxygen, HbS polymerizes, causing red blood cells to become sickle-shaped.

 Genetics

• Autosomal recessive inheritance
• HbSS: Sickle Cell Anemia (most severe)
• HbSC, HbSβ-thalassemia: Milder forms
• Carrier state (HbAS): Sickle Cell Trait — usually asymptomatic

🌍 Epidemiology

• Common in Sub-Saharan Africa, Middle East, India, Mediterranean
• High prevalence due to protective effect against malaria
• Symptoms often begin after 6 months (as fetal Hb declines)

🧪 Pathophysiology

• Deoxygenation → HbS polymerizes → RBCs sickle
• Sickled cells are rigid, sticky, and prone to hemolysis and vaso-occlusion
• Leads to anemia, ischemia, infarction, and organ damage

Sickled RBCs in blood vessel 

Types of Crises in Sickle Cell Disease

Sickle cell crises are acute events caused by sickling of red blood cells, leading to obstruction of blood vessels, tissue ischemia, and various complications.

 1. Vaso-Occlusive Crisis (Pain Crisis)

• Most common type of crisis
• Caused by obstruction of microcirculation by sickled RBCs
• Presents with severe pain in bones, joints, chest, or abdomen
• Often triggered by cold, dehydration, stress, infection
• Management: hydration, analgesics (NSAIDs, opioids), oxygen if hypoxic

2. Acute Chest Syndrome

• Life-threatening complication
• Causes: infection, fat embolism, or pulmonary infarction
• Presents with chest pain, fever, cough, hypoxia, dyspnea
• Diagnosis: chest X-ray shows new infiltrate
• Management: oxygen, antibiotics, analgesia, blood transfusion

 3. Sequestration Crisis

• Sudden pooling of blood in spleen or liver
• Common in infants and young children
• Leads to hypovolemic shock and severe anemia
• Spleen is usually enlarged and tender
• Management: urgent blood transfusion, IV fluids
• May require splenectomy if recurrent

 4. Aplastic Crisis

• Caused by transient suppression of bone marrow, usually by Parvovirus B19
• Leads to sudden severe anemia with low reticulocyte count
• No splenomegaly or pain
• Management: blood transfusion, monitor for infection control

 5. Hemolytic Crisis

• Acute acceleration of hemolysis
• Presents with jaundice, pallor, dark urine, fatigue
• Management: supportive care, transfusion if severe

🧒 Clinical Features

A. Chronic Hemolytic Anemia

• Fatigue, pallor, jaundice, gallstones
• Delayed growth and puberty

B. Vaso-Occlusive Crises

• Pain in bones, chest, abdomen (especially long bones and joints)
• Often triggered by cold, dehydration, infection, stress

C. Dactylitis

• Swelling of hands and feet — often first manifestation in infants

D. Acute Chest Syndrome

• Fever, chest pain, cough, hypoxia
• Can be life-threatening

E. Stroke

• Common in children, especially without prophylaxis
• Silent infarcts → cognitive decline

F. Infections

• Functional asplenia → high risk of pneumococcal and Salmonella infections

G. Other Features

• Priapism, leg ulcers, retinopathy, renal dysfunction

Diagnosis

• Hemoglobin electrophoresis (confirms HbS)
• Peripheral blood smear: sickled RBCs, target cells
• CBC: anemia with high reticulocyte count
• Newborn screening: mandatory in many countries
• Transcranial Doppler (TCD): screens for stroke risk in children

Management

1. Acute Management

• Hydration, oxygen, analgesia (NSAIDs or opioids) for pain crises
• Antibiotics and oxygen for acute chest syndrome
• Blood transfusions for severe anemia, stroke prevention, pre-surgery

Chronic Management

• Folic acid supplementation
• Hydroxyurea: increases HbF, reduces crises
• Penicillin prophylaxis: from 2 months to 5 years of age
• Vaccinations: pneumococcal, Hib, meningococcal, annual influenza
• Chronic transfusions: for stroke prevention or severe disease
• Bone marrow transplant: only curative option (in selected cases)

⚠️ Complications

• Stroke, acute chest syndrome
• Osteomyelitis (especially Salmonella)
• Splenic sequestration crisis
• Gallstones, kidney injury
• Retinopathy, avascular necrosis