Developmental disabilities are birth defects that are enduring impairments to physical or cognitive functioning. Individuals with a developmental disability may have difficulty with learning, language, coordinating body movements, mobility and living independently. According to a report authored by Dr. Sheryl Larson, et al, in the April 2000 issue of "MR/DD Data Brief," about 15 in 1,000 people have a developmental disability.
Degenerative Disorders
Individuals with degenerative disorders typically appear to have healthy development during infancy, but begin to lose functions or abilities later in childhood. Although people with degenerative disorders are born with the condition, impairments are usually not seen until the person begins to show loss of functioning. Physical, sensory and mental difficulties may occur among those with a degenerative disorder. One example of a degenerative disorder is Rett's disorder, which is marked with a decline in functioning between the ages of 3 months and 3 years. Rett's disorder typically affects females. Children with Rett's disorder often wring their hands and may have declines in intellectual abilities, movement and communication skills.
Metabolic Disorders
Metabolic disorders affect metabolism, or the way the body converts food into energy for everything the body does. Hypothyroidism is a metabolic disorder that occurs when the thyroid gland does not produce enough hormones to meet the necessary functions of the body. Some of these bodily functions include metabolism, breathing, brain development, body temperature, weight and women's menstrual cycles. Having limited thyroid hormones slows down bodily functions. Untreated hypothyroidism in an infant may lead to mental retardation.
Phenylketonuria, or PKU, is a metabolic disorder in which the body is unable to use an amino acid called phenylalanine. Individuals with PKU may have a smaller head size, have lighter skin and hair when compared to other family members, and experience difficulties with cognition, hyperactivity, social skills and seizures.
Nervous System Disorders
Nervous system disorders affect the brain, spinal cord and nerves. Individuals with a nervous system disorder may have difficulty with movement, speech, learning and seizures. Spina bifida is a nervous system disorder that occurs when the brain, spinal cord or protective covering surrounding the brain and spinal cord, or meninges, do not completely develop. Mental retardation is another nervous system disorder, and is characterized by below-average intelligence and impairments with social skills, language and self-care abilities. Down syndrome is a type of mental retardation that is caused by having an additional copy of chromosome 21.
Disabilities of the Senses
Sensory-related disabilities are a part of complicated birth defects and are characterized by impairments to the senses, such as seeing, hearing or feeling. Infants with congenital rubella syndrome may be deaf and develop cataracts of the eyes. Congenital rubella syndrome may develop in a fetus when the mother has rubella during the first three months of pregnancy.
Another sensory-related disability is seen among individuals with Fragile X syndrome, which is a genetic condition that causes no amount or low amounts of a particular protein that is involved in brain development. Individuals with Fragile X syndrome are usually sensitive to loud sounds and may have outbursts when hearing loud noises.
References
- "Categories of Disability Under IDEA"; National Dissemination Center for Children with Disabilities; April 2009
- "Handbook of Developmental Disabilities"; Samuel Odom, Robert Horner, Martha Snell, and Jan Blacher; 2009
- "MR/DD Data Brief"; Prevalence of Mental Retardation and/or Developmental Disabilities: Analysis of the 1994/1995 NHIS-D; Sheryl Larson, Charlie Lakin, Lynda Anderson, Nahoon Kwak, Jeoung Hak Lee, and Deborah Anderson; April 2000
