[<< wikibooks] Handbook of Genetic Counseling/Developmental Delay and Mental Retardation
Developmental Delay and Mental Retardation

== Etiology ==
Cause unknown in about 50% of cases
Often multifactorial with genetic and environmental components
Low birth weight, prematurity, and perinatal complications may be associated - not known if they cause mental retardation or if factor causing these problems also caused MR
Approximately 2000 known genetic causes
Chromosomal abnormalities
Metabolic or endocrine disorders
Hereditary degenerative disorders
Hormonal deficiency
Hereditary syndromes or malformations
Acquired causes
Prenatal: infection, irradiation, or exposure to toxins
Perinatal: prematurity, anoxia, cerebral damage, or infection
Postnatal: brain injuries, anoxia, poisons, hormonal deficiencies, metabolic dysfunction, postimmunization encephalopathy, sociocultural, kernicterus, epilepsy
In United States, 1-3% of people meet cognitive and functional criteria

== Clinical Features ==
It is a, medical and mental, developmental disorder
Affects developmental and cognitive abilities
Substantial limitations in functioning
IQ scores below 70
Mild MR: IQ range 50-55 to 70
Moderate MR: IQ range 35-40 to 50-55
Severe MR: 20-25 to 35-40
Profound MR: Below 20-25
Majority of individuals with mental retardation have IQ scores of 55-69
Able to live independently or with support in group homes
Less than 10% of all people with mental retardation have severe to profound impairments
May have limited ability to develop some adaptive skills
Home living
Social/interpersonal skills
Functional academic skills
Health and safety
Use of community resources
Can affect abilities in key developmental areas
Language development
Visual and auditory perception and discrimination
Abstract problem solving
Onset must occur before age 18

== Management options ==
No treatment or cure
Early intervention services
Provided by the county in Ohio to children between birth and age 3
Studies show the earliest experiences in learning sets the pattern for later information processing
Begins with comprehensive developmental assessment
May be performed here by CCDD or by private service
Assessment used to develop intervention strategy
After age 3, school system provides special services
Develop an Individualized Education Plan (IEP)
Early education focuses on cognitive development and special services such as speech therapy
Later education may focus on developing life skills
Can attend school until age 21
Adult services
Handled in Ohio by the Board of MRDD
Focuses on job training, vocational education
Community or group homes are available for semi-independent living

== Recurrence Risks ==
Can calculate a much more accurate risk if etiology is known
Other factors to consider:
Possibility of consanguinity
Whether one or both parents are affected
Developmental disabilities may be exacerbated by environmental factors
Unsafe or unstimulating home environment
Substandard health care
Unadequate schooling or lack of services
Empiric risk figures when parents affected with mental retardation of unknown etiology
39.4% if both parents affected
7.8% if only father affected
19.6% if only mother affected (higher due to prevalence of X-linked inheritance for conditions such as Fragile X)

== Psychosocial Issues ==
Provision of adequate services
Burden of taking care of a child/adolescent/adult with mental retardation
Impact on siblings and other family members
Denial, grief, disappointment, or feeling of loss
Interruption of career goals, family routines, or plans for the future
Financial and insurance issues

== References ==
Milunsky, Aubry. Prevention of Genetic Disease and Mental Retardation. Philadelphia: W.B. Saunders Company (1975).

== Notes ==
The information in this outline was last updated in 2001.