Sickle Cell Disease (SCD)

Genetics and Sickle Cell Disease

Sickle Cell Disease is a group of inherited disorders that affect the hemoglobin protein found in red blood cells. This disease causes the red blood cells to be hard, sticky, and shaped like a sickle (like a crooked banana). Normal red blood cells are soft, smooth, and round and last about 120 days. Sickle red blood cells only last about 20 days.

Usually, individuals receive two copies of the hemoglobin A gene, one from each parent. Individuals with Sickle Cell Disease do not have any copies of the hemoglobin A gene. Instead, these individuals have received two copies of an alternative form of the hemoglobin gene. At least one of those two alternative genes must be hemoglobin S in order to result in Sickle Cell Disease. The following section describes the various types of sickle cell disease and what genes those individuals carry.

Types of Sickle Cell Disease

There are three main types of sickle cell disease:

  • Hemoglobin SS disease: Individuals have received two copies of the hemoglobin S gene.
  • Hemoglobin SC disease: Individuals have received one copy of the hemoglobin S gene and one copy of the hemoglobin C gene.
  • Hemoglobin SB (beta) Thalassemia disease including SB0 (beta zero) and SB+ Thalassemia disease: Individuals have received one copy of the hemoglobin S gene and one copy of the hemoglobin beta- thalassemia gene. The beta-thalassemia genes result in reduced (B+) or lack of expression (B0) of normal hemoglobin A, resulting in a person either having only hemoglobin S or mostly hemoglobin S with a small percent of normal hemoglobin A.

Rarely, a person has one gene for hemoglobin S and another for a rarer form of hemoglobin, such as hemoglobin O. The most common type of Sickle Cell Disease is hemoglobin SS disease.

What is Sickle Cell Trait?

When an individual receives a copy of hemoglobin A from one parent and a copy of hemoglobin S from the other parent, the result is Sickle Cell Trait. Sickle Cell Trait is not a disease and does not change into Sickle Cell Disease later on in life. However, if two individuals with Sickle Cell Trait have a child together, that child is at risk (25%) for having Sickle Cell Disease.

Outcome-Modifying Genes in Sickle Cell Disease

Dr. Marilyn Telen and Duke University Health System are conducting a National Institute of Health-sponsored research study to determine if certain hereditary factors may be related to specific complications of Sickle Cell Disease.

The Duke Molecular Physiology Institute (DMPI), formerly the Duke Center for Human Genetics, and the Duke Comprehensive Sickle Cell Center hope that information learned from this research study will make ways for better prevention and treatment of the debilitating complications of Sickle Cell Disease (stroke, heart failure, kidney failure, leg ulcer, eye failure, joint disease, chronic pain, psychosocial strain, anemia, lung disease, and more).

The Duke researchers will examine the genetic material (DNA) from 1,000 adult patients with Sickle Cell Disease. The genetic material of individuals with a particular complication (such as stroke) will be compared with individuals who do not have that complication. The genetic differences found between those groups may explain why some patients with Sickle Cell Disease develop strokes while others develop kidney failure or leg ulcers or heart failure.

Sickle Cell Disease Study Participation

Patients who participate in this study should be 18 years or older, male or female, with Sickle Cell Disease (HbSS or SB0 Thalassemia) and have agreed to:

  • One interview to review medical history and to collect environmental information that may affect Sickle Cell Disease.
  • A review of the patient’s medical record to complete the medical history.
  • One routine physical examination as well as laboratory tests routinely performed by physicians to assess the severity of the disease.
  • The removal once of up to 24cc of blood by venipuncture.
  • The use of a portion of the blood removed for genetic studies to identify differences in specific genes that may affect the complications and severity of Sickle Cell Disease.

Study participation normally requires a single clinic visit. On occasion during the completion of the medical history, patients may be contacted by phone by the study coordinator to help clarify certain information obtained during the interview. Patients who recently have not been routinely followed by a clinic doctor or a primary care physician may be advised to seek a clinic or primary care physician in the community who can assess the severity of their Sickle Cell Disease and provide them with adequate medical care. Finally, patients may choose to receive by mail the yearly newsletter that will inform them of the progress made in the study.

To participate in the study please contact:

Clinical Coordinator
Jude C. Jonassaint, RN
Duke University Department of Medicine
Division of Hematology
Duke University Comprehensive Sickle Cell Center
Phone: (919) 668-6035
Phone: (919) 684-6464

Principal Investigator
Marilyn J.Telen, MD
Professor and Chief
Division of Hematology
Duke University Department of Medicine
DUMC Box 2615
Durham, NC 27710.

Sickle Cell Disease Management Resources

The DMPI and Duke Comprehensive Sickle Cell Center researchers have compiled a list of sickle cell disease management resources to assist patients and families.

Sickle Cell Disease Publications

  • For Health Care Workers: The Management of Sickle Cell Disease
    National Institute of Health, Division of Blood Diseases and Resources.This book offers information for health care workers based on evidence or clinical practice relating to Diagnosis and Counseling, Health Maintenance, Treatment of Acute and Chronic Complications, Contraception and Pregnancy, and Anesthesia and Surgery.
  • For School Teachers: Sickle Cell Disease: The Teacher Can Make a Difference
    William H. Schultz, PA-C, MHS; M. Anita Holmes, JD, MPH; Mary Abrams, MPH; Thomas R. Kinney, MD. Duke Comprehensive Sickle Cell Center, Duke University Medical Center, Durham, NC 27710.Although this book is intended for school teachers, parents and school counselors will find in it invaluable information about foreseeing problems that children with Sickle Cell Disease may have in school.

    For more information on this book, contact:

    Elaine Whitworth
    Director, Education Division
    Duke University Comprehensive Sickle Cell Center
    DUMC Box 3939
    Durham, NC 27710
    Phone: (919) 684-6464

  • For North Carolina Health Care Providers: Guideline for Care in Sickle Cell Disease prepared by the North Carolina Sickle Cell Disease Consortium, provides information on managing care in Sickle Cell Disease with
    an excellent overview of psychosocial concerns.For more information on this book, contact:

    Elaine Whitworth
    Director, Education Division
    Duke University Comprehensive Sickle Cell Center
    DUMC Box 3939
    Durham, NC 27710
    Phone: (919) 684-6464

SCD Support Organizations in North Carolina

Women’s & Children’s Health Section
1916 Mail Service Center
Raleigh, NC 27699-1916
Phone (919) 715-7937 Fax (919) 715-3925

The State of North Carolina-Women’s and Children’s Health Section features six Regional Offices with at least one consultant representing the following fields:

  • Child Health Nursing
  • Nutrition Services
  • Sickle Cell Education
  • Genetic Counseling
  • Physical Therapy
  • Social Work
  • Immunization
  • School Health Nursing
  • Women’s Health Nursing

Regional Offices:

852 Merrimon Ave
Asheville, NC 28804
Phone: (828) 251-6771
Fax: (828) 251-6770

919 N. Main St
Mooresville, NC 28115
Phone: (704) 663-1699
Fax: (704) 799-1427

943 Washington Square Mall
Washington, NC 27889
Phone: (252) 946-6481
Fax: (252) 975-3716

225 Green St
Fayetteville, NC 28301
Phone: (910) 486-1191
Fax: (910) 486-1477

3800 Barrett St
Raleigh, NC 27609
Phone: (919) 571-4700
Fax: (919) 571-4718

585 Waughtown St
Winston-Salem, NC 27107
Phone: (336) 771-4600
Fax: (336) 771-4633

Piedmont Health Services and Sickle Sickle Cell Agency (PHSSCA)
Information and services for sickle cell patients in the Greensboro NC area.

SCD Resources in the Duke University Area
Duke University Comprehensive Sickle Cell Center provides services for both children and adults.

Duke University Comprehensive Sickle Cell Center
Box 3939, DUMC
Durham, NC 27710
Phone: (919) 684-6464
Fax: (919) 681-6174

Duke’s Consultation and Referral Center 
Phone: (toll free) (888) ASK-DUKE (275-3853).

Bridges Pointe Foundation
Community outreach service affiliated with the Duke University Comprehensive Sickle Cell Center. The organization seeks to promote the development of supportive services for young adults with sickle cell disease, to empower them for independent living, and to enhance their quality of life by providing: affordable shelter, case management, comprehensive education, an employment and training program, computer training, psychosocial interventions, self-care and health education.

Partners in the Outcome Modifying Gene in Sickle Cell Disease

University of North Carolina Comprehensive Sickle Cell Program
University of North Carolina at Chapel Hill
101 Manning Dr, CB#7005
General Clinical Research Center, Room 7005
Chapel Hill, NC 27599-7005
Phone: (toll free) (800) 476-6876
Phone: (919) 966-0178
Fax: (919) 843-7693

Georgia Comprehensive Sickle Center
Center at Grady Memorial Hospital
80 Jesse Hill, Jr. Dr SE
Atlanta, GA 30303
Phone: (404) 616-3572

The Georgia Comprehensive Sickle Center offers excellent information and education for patients, families, volunteers, and professionals.

Additional Sickle Cell Disease Information

Note: the DMPI neither endorses the information nor supports the programs offered by these organizations. The DMPI does not assume responsibility for the content found in the following web links. An association with the organizations represented should not be implied.

SCD Information & Support Organizations

Genetics of Sickle Cell Disorder

Sickle Cell Disorder Clinical Trials

SCD Pharmaceutical Information

  • Rx Assist provides health care provider information on accessing more than 100 pharmaceutical manufacturers’ patient assistance programs. These programs usually offer a limited supply of free prescription medication to eligible patients.

Sickle Cell Disorder Publications and Articles

The National Maternal and Child Health Clearinghouse has the following titles:

Sites for Kids

Information in Other Languages



International Sickle Cell Sites