Handbook of Genetic Counseling/Sickle Cell Anemia

Sickle Cell Anemia

Introduction

• Determine what the patient already knows about sickle cell
• Assess what concerns the patient wants to address today

What is sickle cell disease?

• inherited blood disorder affecting the oxygen carrying part of the blood cells called hemoglobin
• hemoglobin in sickle cell anemia forms a "sickle" or banana shape
  • normal hemoglobin is called hemoglobin A
  • sickle cell hemoglobin is called hemoglobin S
• this shape causes it to be broken down in the liver leading to not enough blood cells
• people with sickle cell disease experience pain, damage to organs, and sometimes early death
  • this is due to sickle shaped blood cells blocking tiny blood vessels
  • this leads to prevention of blood flow to certain areas of the body

Diagnosis

• diagnosis is made by a blood test called hemoglobin electrophoresis
  • those with mostly hemoglobin S have sickle cell disease
  • those with only hemoglobin A do not have sickle cell disease
  • those with both hemoglobin A and hemoglobin S are heterozygote carriers and have sickle cell trait
    • this means they are carriers of the sickle cell gene
    • they generally do not have any health problems but can pass the gene to their children
  • this test requires 3cc of blood in a red-capped EDTA tube
  • prenatal testing is also available
  • in Ohio children are now tested for sickle cell as part of the newborn screening program

Symptoms

• chronic hemolytic anemia - may lead to reduction in energy and cause growth retardation
• Vaso-occlusion - blockage of small blood vessels that may lead to pain and tissue damage.
• Splenic sequestration - increase in spleen size due to storage of red blood cells
• Organ failure - may result from insufficient blood flow later in life
• other problems may arise such as neurological effects, stroke, chronic eye disease, renal disease, and leg ulcers

Treatment

• mainly symptomatic
• drugs such as hydroxyurea are used to increase fetal hemoglobin
• vasodilators and lubricants used to prevent microvascular blockage with very little success

Inheritance

• Sickle cell disease is inherited in an autosomal recessive fashion
  • people with sickle cell disease have two copies of the mutated gene
  • people with sickle cell trait have one normal gene and one mutated gene
• Parents who both have sickle cell trait will have a 25% chance of having a child with sickle cell disease, a 50% chance of having a child with sickle cell trait, and a 25% chance of having a normal child who is not a carrier
• If one parent has sickle cell disease and one parent has sickle cell trait, they have a 50% chance of having a child with sickle cell disease but the child will have sickle cell trait.
• If one parent has sickle cell disease and the other parent is normal the child will have sickle cell trait but 0% chance of having sickle cell disease.

Clarification: In order for a child to have sickle cell disease both parents must have at least one copy of the abnormal sickle cell gene, or in other words both parents must have sickle cell trait for the child to have sickle cell disease.

Population Genetics

• African-Americans: 1/12 are carriers
• 1/400-600 children are born with sickle cell disease
• People of Hispanic, Greek, Italian, Arabic, and Asian Indian also have high carrier rates

Psychosocial Issues

• Guilt over passing on trait to children
• people with sickle cell trait may be treated as though they are sick despite having no symptoms
• people with sickle cell trait may also be more worried about their health despite having no symptoms
• worry over reproductive decisions

Resources

• CHMC Cincinnati Comprehensive Sickle Cell Center

513-636-4541

333 Burnett Avenue

Cincinnati, OH 45229

• The Ohio Sickle Cell Affected Families Association, Inc.

141 Tishman Street

Columbus, OH 43228

614-272-1516

• National Association for Sickle Cell Disease, Inc.

3345 Wilshire Blvd., Suite 1106

Los Angeles, CA 90010-1880

213-736-5455

800-524-7802

References

• Headings, Verle E. "Psychosocial Issues in Sickle Cell Counseling" Genetic Counseling: Psychosocial Dimensions. 1979.
• March of Dimes Public Health Education Information Sheet. Sickle Cell Disease.
• Koshy, Mabel. "Sickle Cell Disease" University of Chicago
• Ricknagel, D. "Sickle Cell Syndromes"

Notes

The information in this outline was last updated in 2002.