Sickle cell anemia is one of a group of inherited disorders known as sickle cell disease. It affects the shape of red blood cells, which carry oxygen to all parts of the body. Red blood cells are usually round and flexible, so they move easily through blood vessels.
Sickle cell anemia is characterized by the replacement of glutamate by valine at the 6th position.
Sickle cell anemia is an autosomal recessive disorder occurring due to the T-to-A point mutation in the sixth codon of the β-globin gene. This results in the replacement of glutamate residue with valine. This leads to the formation of sickle-shaped red blood cells due to the polymerization of deoxygenated hemoglobin (HbS).
The clinical features of sickle cell disease are due to the tendency of HbS molecules to stack into polymers when deoxygenated. The features are:

Moderately severe hemolytic anemia with jaundice.
Painful bone crisis- hand-foot syndrome or dactylitis of the bones of hands and feet.
Acute chest syndrome typically presents with fever, cough, chest pain, and pulmonary infiltrates.
Hyposthenuria- inability to concentrate urine.
Aplastic crisis stems from the infection of red cell progenitors by parvovirus B19, which causes a transient cessation of erythropoiesis and a sudden worsening of the anemia.
Spleen

i) In children- splenic sequestration crises occur which results in splenomegaly due to red pulp congestion.

ii) Adolescence or early adulthood- auto splenectomy occurs due to splenic infarction, fibrosis, and progressive shrinkage.

iii) Increased susceptibility to infection with encapsulated organisms like pneumococcal, meningococcal, and Haemophilus influenza septicemia, but can be reduced by vaccination and prophylactic antibiotics.

7.Other clinical features include priapism, leg ulcers, stroke, retinopathy, pigment gallstones, and growth retardation.

The diagnosis is suggested by the clinical findings, the presence of irreversibly sickled RBCs on peripheral smear, and hemoglobin electrophoresis showing increased HbA2, HbF, and S spike.
Disease-modifying drugs such as hydroxyurea can be given to patients with sickle cell anemia since it reduces the incidence of adverse vaso-occlusive vents. Blood transfusions are used to treat and prevent complications of sickle cell disease, including preparation for surgery, symptomatic anemia, acute stroke, multi-organ failure, and acute chest syndrome

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Hematology: Red Blood Cells

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