What are developmental disabilities?
Developmental disabilities are birth defects related to a problem with how a body part or body system works. They may also be known as functional birth defects. Many of these conditions affect multiple body parts or systems.
What are the different types of developmental disabilities?
Nervous system disabilities
These are birth defects that affect the functioning of the brain, spinal cord, and nervous system, which can impact intelligence and learning. These conditions can also cause problems such as behavioral disorders, speech or language difficulties, convulsions, and movement disorders. Some of the common nervous system disabilities include:
- Mental retardation - The term mental retardation describes a certain range of scores on an IQ (intelligence quotient) test. Mental retardation can result from a number of different conditions, including (but not limited to):
- Down syndrome - a set of mental and physical characteristics related to having an extra copy of Chromosome 21.
- Fragile X syndrome- the most common inherited form of mental retardation caused by a defect in a specific part of the Fragile X Mental Retardation-1 gene that causes the body to produce low amounts or none of a certain protein. Without the protein, the brain doesn't develop normally.
- Autism Spectrum Disorders - a range of problems that can affect a person's communication skills, social skills, and intelligence. Because autism is diagnosed on a spectrum, people with this condition can have mild symptoms or severe symptoms; but they all have a type of autism.
Sensory-related disabilities Sensory-related problems are often a key part of complex birth defect patterns. For instance:
- Children with congenital rubella are likely to be deaf, and to develop cataracts of the eyes.
- Children with Williams syndrome have trouble seeing spatial relationships between objects around them.
- Those with Fragile X syndrome are often very sensitive to loud noises; they may overreact or have outbursts in reaction to such sounds.
This group of functional birth defects affects a person's metabolism, which is the way the body builds up, breaks down, and otherwise processes the materials it needs to function. For example, how your body breaks down sugar to create energy is a metabolic process. Two commonly known metabolic disorders include:
- Phenylketonuria (PKU) - a condition in which a problem with a specific enzyme, a protein that speeds up certain chemical reactions, causes mental retardation.
- Hypothyroidism - a hormonal condition that, if left untreated in an infant, can cause mental retardation.
Some infants born with degenerative disorders appear normal at birth, but then lose abilities or functions due to the in condition. In these cases, the defect is usually not detected until an older age, when the child or person starts to show signs of loss of function. Some degenerative disorders are the result of metabolic disorders.
Degenerative disorders can cause physical, mental, and sensory problems, depending on the specific defect. Rett syndrome is an example of a degenerative birth defect. This disorder, which usually affects girls, is most often caused by a specific genetic abnormality.
Reprinted with the permission of the National Institute of Child Health and Human Development.
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