SICKLE CELL ANEMIA

Omar and Yassin

DEFINITION

• Sickle cell disease is an inherited blood disorder that is caused by the presence of a mutation in the gene that encodes for the protein, hemoglobin, which carries oxygen to the tissues.

The Normal Hemoglobin Structure

• Consists of four protein subunits: – Two subunits of beta-globin – Two subunits of alpha-globin.

• Each of the four protein subunits carries an iron-containing molecule called heme.

• Heme molecules are necessary for red blood cells to pick up oxygen in the lungs and deliver it to cells throughout the body

• The HBB gene, located on chromosome 11, provides instructions for making a protein called beta-globin.

Hemoglobin in Sickle Cell

• People with this disorder have atypical hemoglobin molecules called hemoglobin S, which can distort red blood cells into a sickle, or crescent, shape.

• They sick together forming long fibers or rods which are stiffer while travelling through the blood vessels.

• Tissue that does not receive a normal blood flow eventually becomes damaged

Causes

Inheritance of Sickle Cell• This condition is inherited in an autosomal recessive pattern, which

means both copies of the gene in each cell have mutations. • The parents of an individual with an autosomal recessive condition

each carry one copy of the mutated gene, their body makes both sickle hemoglobin and normal hemoglobin, but they typically do not show signs and symptoms of the condition.

Example of Inheritance for Sickle Cell Trait.

SYMPTOMS Do not occur until after the

age of 4 months. Blocked blood vessels

painful episodes called crises. May need hospitalization.

Blocked blood vessels Lung, Spleen, Heart damage.

Anemia Fatigue, rapid heart rate, yellowing of eyes, shortness of breath.

Diagnosis

• Hemoglobin Electrophoresis is used to screen for sickle cell disease at birth.– This test uses a sample of blood from infant and

determines what types of hemoglobin are present

Hemoglobin Electrophoresis• Two different types of Hemoglobin are present:

-The A type (normal) -The S type (sickle)• A carrier makes both types.• A person with sickle-cell will have the S-type• A normal person will only have the A-type

Prenatal Diagnosis

• Diagnosis before birth is done by a method called amniocentesis:– Take a sample of amniotic fluid (fluid surrounding baby)

or tissue taken from the placenta (organ that attaches the umbilical cord to the mother's womb) and test it for sickle hemoglobin gene rather than abnormal hemoglobin

• Testing before birth can be done as early as 10 weeks into the pregnancy.

Genetic Counseling

• Individuals who test positive should be informed about the implications for their health and family planning.

• SCT counseling has two components: education and decision-making. – For the first group, the focus is on education, that is, to

enable individuals to make informed decisions, in their own interest, about future family planning.

– For the second group, the focus is on education and informed decisions, in their best interest, about the current pregnancy.

• Counseling should be done by geneticists, master’s degree genetic counselors, social workers, and psychologists.

TREATMENT GOALS

Who Is at Risk for Sickle Cell Anemia?

• Sickle cell anemia is most common in people whose families come from Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia.

• In 2013, sickle cell disease resulted in 176,000 deaths up from 113,000 deaths in 1990.

• Occurs in about 1 out of every 500 African American births. • Also affects Hispanic Americans. Occurs in more than 1 out of

every 36,000 Hispanic American births.• More than 2 million Americans have sickle cell trait. The

condition occurs in about 1 in 12 African Americans.

References

• "Your genes and Your health." cold spring harbor laboratory. N.p., n.d. Web. 8 June 2015. <http://ygyh.org/>.

• "NCBI." National Center for biotechnology information. N.p., n.d. Web. 8 June 2015. <http://www.ncbi.nlm.nih.gov/>.

• "SCDAA." Sickle Cell Disease. N.p., n.d. Web. 8 June 2015.

<http://sicklecelldisease.org/>. • "American Sickle Cell Anemia Association." Ascaa. N.p., n.d.

Web. 8 June 2015. <http://ascaa.org/>. • "Genetics Home Reference." Ghr. N.p., n.d. Web. 8 June 2015.

<http://ghr.nlm.nih.gov/>.