• Autosomal recessive disorder characterized by replacement of the amino acid valine in one of the B chains by glutamic acid.

Pathophysiology

• Hb S deoxygenated polymerization of Hb S molecules rigid strand of hemoglobin molecule sickling of RBCs.

Sickled RBCs

Anemia Vascular occlusions

Clinical manifestations of sickle cell anemia

Sickle cell anemia

Chronic hemolytic anemia

Sickle cell crises

Chronic hemolytic anemia

• Anemia.• Jaundice.• Gall stones.• Hepato-splenomegaly (due to extramedullary

hematopoiesis).

Sickle cell crises

Vaso-occlusive crises

Splenic sequestrationcrisis

Aplastic crisis

Hemolyticcrisis

Vaso-occlusive crises

Stroke

Acute chest syndrome

It is a clinical syndrome characterized by• Chest pain.• Cough• Dyspnea.• Fever.Due to:Chest infection.Fat embolism (secondary to bone infarcts).Pulmonary thrombosis.

Acute abdominal pain

• Due to splenic infarct.

Priapism

• Painful sustained unwanted erection.• Due to veno-occlusion resulting in blood

trapping in erectile Priapism tissue.

Priapus

Dactylitis

• Painful swollen fingers or toes due to bone infarction.

Splenic sequestration crisis

• Acute painful enlargement of the spleen.• Associated with drop in RBCs & platelet

counts.• Due to sudden pooling of large amounts of

blood into the spleen.

Aplastic crisis

• Acute reticulocytopenia triggered by papovirus B19.

Hemolytic crisis

• Acute acclerated drop in hemoglobin level.• Occur in patients with co-existent G6PD

deficiency.

Chest • Lung:• Consolidation due to chest infection.• Heart:• Cardiomegaly and heart failure due

to increased cardiac out put.• Mediastinum:• Posterior mediastinal mass lesion

due to extramedullary hemopoiesis.

Spleen

• Splenic infarct.• Autosplenectomy (small calcified spleen).

Liver

Hepatomegaly: • Due to extramedullary hemopiesis.Hepatic siderosis:• due to repeated transfusion & iron overload

Gall bladder

• Gall stones.• Biliary sludge.

Kidney

• Renal papillary necrosis.• Renal infarcts.

Skeletal manifestations of sickle cell anemia

• Bone marrow hyperplasia.• Bone infarction.• Bone infection.• Growth disturbances.

Bone marrow hyperplasia

• Less sever than thalassemia.

Long bones• Diffuse osteoporosis,• Medullary expansion,• Cortical thinning,• Coarse trabeculations (honey comb)• (reactive sclerosis of the secondary trabeculae after

destruction of the primary trabeculae), • Endosteal apposition, (another response to

destruction of the medullary trabeculae by inward cortical thickening, then cortical splitting giving bone within bone appearance). &

• Wide vascular channels.

• MRI:• Diffuse low signal on T1 & T2 WIs • (due to persistent red marrow).

• Bone scan:• Diffuse symmetrical increased uptake.

Skull

Skull

Bone infarction

Hand & foot syndrome

Bone infection

• Salmonella osteomyelitis.• Salmonella spondylodiscitis.

Premature fusion of the epiphysis

Premature fusion of the epiphysis & osteomyelitis