Sickle Cell Disease (SCD)

Excerpts from Social Security Ruling 17-3p

See the full text at https://www.ssa.gov/OP_Home/rulings/di/01/SSR2017-03-di-01.html

SCD is the most common inherited blood disease in the United States, affecting an estimated 100,000 Americans.SCD is not always easy to evaluate due to its varying nature and complications. In this SSR, we provide basic information about SCD and its variants and clarify that sickle cell trait is not a variant of SCD. We also provide guidance for assessing SCD under the hematological disorder listings and determining how this impairment may affect the residual functional capacity finding for adults and the functional equivalence finding for children.

Policy Interpretation

We consider all medical evidence when we evaluate a claim for disability benefits. The following information is in a question and answer format that provides guidance about SCD and how to consider evidence regarding this impairment. Questions 1 and 2 provide basic background information about SCD and its variants. Question 3 clarifies that sickle cell trait is not a variant of SCD. Question 4 discusses the complications and symptoms of SCD. Questions 5 through 7 explain how adjudicators should evaluate SCD at various points of the adjudication process, including the adult and child hematological listings we consider.

1. What is SCD?

SCD is a type of hemolytic anemia and an inherited hematological disorder that affects the hemoglobin within a person's red blood cells (RBC). Hemoglobin is the protein within RBC that carries oxygen. The abnormal hemoglobin makes the RBC more prone to distortion (“sickling”), which results in blocked blood vessels and a shortened RBC lifespan. Hemolytic anemia results when the abnormal RBC are destroyed faster than the body can produce them.

When hemoglobin is normal, a person's RBC are round and easily travel through blood vessels, bringing oxygen to the body's organs and tissues. SCD causes sickle-shaped RBC that are not flexible and can stick to vessel walls, causing blockages (vaso-occlusion) that slow or stop the flow of blood and oxygen. This blockage may in turn cause pain. Persons with SCD are predisposed to pain, infection, and other complications. Because people inherit SCD, the disease is present at birth, but the age when children display symptoms varies.

2. What are the different variants of SCD?

The different variants of SCD may indicate the severity of complications and the resulting functional limitations caused by SCD. Laboratory blood tests such as hemoglobin electrophoresis establish the existence and the variants of SCD. The following are the most common variants of SCD:

o Hemoglobin (Hb) SS (HbSS) — a person with this form of SCD inherits one sickle cell gene from each parent. HbSS is the most common and usually most severe form of SCD.

o HbSC — a person inherits one sickle cell gene from one parent, and another gene for an abnormal hemoglobin called “C” from the other parent. HbSC is usually a milder type of SCD.

o Hb S-beta (Sβ) thalassemia — a person inherits one sickle cell gene from one parent, and a gene for beta thalassemia from the other parent. There are two forms of beta thalassemia, sickle beta zero thalassemia (Hb Sβ0 thalassemia) and sickle beta plus thalassemia (Hb Sβ+ thalassemia). Sickle beta zero thalassemia is usually a more severe form of SCD. People with sickle beta plus thalassemia tend to have a milder form of SCD.

o HbSD, HbSE, and HbSO— people with these variants of SCD have one sickle cell gene plus another abnormal hemoglobin gene, “D,” “E,” or “O.” These are rarer types of SCD with varying severity.

3. Is sickle cell trait a variant of SCD?

No. Sickle cell trait is not a variant of SCD. Sickle cell trait occurs when a person inherits one sickle hemoglobin gene from one parent and a normal gene from the other parent. People with sickle cell trait rarely have signs and symptoms associated with SCD and usually do not need treatment. However, in rare cases and under extreme conditions such as intense exercise, people with sickle cell trait have a higher risk of severe breakdown of muscle tissue (exertional rhabdomyolysis) that can lead to serious complications. In spite of this higher risk, recent evidence indicates that sickle cell trait is not associated with an increased probability of death.

Sickle cell trait alone is not an impairment. As defined by the Social Security Act, an impairment must result from anatomical, physiological, or psychological abnormalities that can be shown by medically acceptable clinical and laboratory diagnostic techniques. To establish an impairment in this context, we require objective medical evidence (medical signs and laboratory findings) from an acceptable medical source of complications from sickle cell trait. In addition, a person's complications from sickle cell trait must meet the statutory duration requirement, i.e., be expected to result in death or last or be expected to last for a continuous period of not less than 12 months. Therefore, we cannot find a person disabled due to sickle cell trait if there are no medical signs or laboratory findings of complications from sickle cell trait and the complications from sickle cell trait do not meet the duration requirement.

4. What are the common complications and symptoms of SCD?

Complications of SCD may include, but are not limited to pain crises, anemia, osteomyelitis, leg ulcers, pulmonary infections or infarctions, acute chest syndrome, pulmonary hypertension, chronic heart failure, gallbladder disease, liver failure, kidney failure, nephritic syndrome, aplastic crisis, stroke, and mental impairments such as depression. Examples of symptoms that may stem from these complications include pain, fatigue, malaise, shortness of breath, and difficulty feeding in infants. The symptoms of SCD vary from person to person and can change over time.

[Footnotes omitted.]

This SSR is applicable on September 15, 2017.

Federal Register, Vol. 82, No. 178, page 43442