A. What impairment do we evaluate under this body system?

1. General. We evaluate non-mosaic Down syndrome under this body system.

2. What is Down syndrome? Down syndrome is a condition in which there are three copies of chromosome 21 within the cells of the body instead of the normal two copies per cell. The three copies may be separate (trisomy), or one chromosome 21 copy may be attached to a different chromosome (translocation). This extra chromosomal material changes the orderly development of the body and brain. Down;syndrome is characterized by a complex of physical characteristics, delayed physical development, and mental retardation. Down syndrome exists in non-mosaic and mosaic forms.

3. What is non-mosaic Down syndrome?

a. Non-mosaic Down syndrome occurs when you have an extra copy of chromosome 21 in every cell of your body. At least 98 percent of people with Down syndrome have this form (which includes either trisomy or translocation type chromosomal abnormalities). Virtually all cases of non-mosaic Down syndrome affect the mental, neurological, and skeletal systems, and they are often accompanied by heart disease, impaired vision, hearing problems, and other conditions.

b. We evaluate adults with confirmed non-mosaic Down syndrome under 10.06. If you have confirmed non-mosaic Down syndrome, we consider you disabled from birth.

4. What is mosaic Down syndrome?

a. Mosaic Down syndrome occurs when you have some cells with the normal two copies of chromosome 21 and some cells with an extra copy of chromosome 21. When this occurs, there is a mixture of two types of cells. Mosaic Down syndrome occurs in only 1-2 percent of people with Down syndrome, and there is a wide range in the level of severity of the impairment. Mosaic Down syndrome can be profound and disabling, but it can also be so slight as to be undetected clinically.

b. We evaluate adults with confirmed mosaic Down syndrome under the listing criteria in any affected body system(s) on an individual case basis, as described in 10.00C.

B. What documentation do we need to establish that you have non-mosaic Down syndrome?

1. General. We need documentation from an acceptable medical source, as defined in §§ 404.1513(a) and 416.913(a), to establish that you have a medically determinable impairment.

2. Definitive chromosomal analysis. We will find that you have non-mosaic Down syndrome based on a report from an acceptable medical source that indicates that you have the impairment and that includes the actual laboratory report of definitive chromosomal analysis showing that you have the impairment. Definitive chromosomal analysis means karyotype analysis. In this case, we do not additionally require a clinical description of the diagnostic physical features of your impairment.

3. What if we do not have the results of definitive chromosomal analysis? When we do not have the actual laboratory report of definitive chromosomal analysis, we need evidence from an acceptable medical source that includes a clinical description of the diagnostic physical features of Down syndrome, and that is persuasive that a positive diagnosis has been confirmed by definitive chromosomal analysis at some time prior to our evaluation. To be persuasive, the report must state that definitive chromosomal analysis was conducted and that the results confirmed the diagnosis. The report must be consistent with other evidence in your case record; for example, evidence showing your limitations in adaptive functioning or signs of a mental disorder that can be associated with non-mosaic Down syndrome, your educational history, or the results of psychological testing.

C. How do we evaluate other impairments that affect multiple body systems?

1. Non-mosaic Down syndrome (10.06) is an example of an impairment that commonly affects multiple body systems and that we consider significant enough to prevent you from doing any gainful activity. If you have a different severe impairment(s) that affects multiple body systems, we must also consider whether your impairment(s) meets the criteria of a listing in another body system.

2. There are many other impairments that can cause deviation from, or interruption of, the normal function of the body or interfere with development; for example, congenital anomalies, chromosomal disorders, dysmorphic syndromes, metabolic disorders, and perinatal infectious diseases. In these impairments, the degree of deviation or interruption may vary widely from individual to individual. Therefore, the resulting functional limitations and the progression of those limitations also vary widely. For this reason, we evaluate the specific effects of these impairments on you under the listing criteria in any affected body system(s) on an individual case basis. Examples of such impairments include trisomy X syndrome (XXX syndrome), fragile X syndrome, phenylketonuria (PKU), caudal regression syndrome, and fetal alcohol syndrome.

3. If you have a severe medically determinable impairment(s) that does not meet a listing, we will consider whether your impairment(s) medically equals a listing. (See §§ 404.1526 and 416.926.) If your impairment(s) does not meet or medically equal a listing, you may or may not have the residual functional capacity to engage in substantial gainful activity. In that situation, we proceed to the fourth and, if necessary, the fifth step of the sequential evaluation process in §§ 404.1520 and 416.920. We use the rules in §§ 404.1594 and 416.994, as appropriate, when we decide whether you continue to be disabled.

10.01 Category of Impairments, Impairments That Affect Multiple Body Systems

10.06 Non-mosaic Down syndrome, established as described in 10.00B.