2. Definition
Significantly sub-average intellectual function
existing concurrently with deficits in adaptive
behavior (communication, self care, self
direction) and manifested during the
developmental period.
Incidence: about 2% of population.
3. Classification
Mild: IQ 55-70, represent 80% or retarded
children. As adults they can marry, live
independently, be employed, and have
functional reading and writing. The major
deficits are in Judgment.
Moderate: IQ 40-55. represent 12%. They
require continuous supervision and economic
support. They are capable of self care and
employment in a sheltered setting.
4. Cont. Classification
Sever: IQ 25-40, represent 7% of retarded.
They are totally economically dependent and
need close supervision. They may acquire
language and can be trained in elementary
self care skills.
Profound: IQ level less than 25. Represent
1%. They have limited communication and
self care skills. They require highly structured
environment with continuous supervision.
5. Etiology
Mild MR is more prevalent in lower
socioeconomic groups and rarely explained
by a biologic cause, while moderate and
sever MR are more evenly distributed
through all socioeconomic classes and more
frequently tend to have a biological cause.
6. Conditions associated with MR
Period of development Type of condition Examples
Preconception and Metabolic Hurler syndrome
Periconception Malformation Encephalocele
Chromosomal Down syndrome
Prenatal Teratogen Chemicals
Infection Rubella
Perinatal Prematurity Hypoxia
metabolic hypoglycemia
postnatal Infection Meningitis
Trauma Car accidents
Malnutrition Kwashiokor
Metabolic Phenylketonuria
toxin Lead toxicity
7. Assessment
History: family pedigree and details of
pregnancy, delivery and postnatal period.
Physical examination: head circumference,
dysmorphic features, and associated
anomalies.
Developmental testing.
