What is mental retardation? It is the failure to develop normal mental capacities. We can use test of intelligence such as the Wechsler Preshool, the Standfor- Binet IQ and Primary Scale of Intellgence-Revised to classify mental retardation. Normal IQ is 100 and have standard deviation of 15.

The classification of mental retardation:

1. Mild: IQ between 50 and 70.
2. Moderate: IQ between 40 and 55.
3. Severe: IQ between 25 and 40.
4. Profound: IQ less than 25.

There are many etiologies of mental retardation. Trauma of prenatal and postnatal, infection, abnormalities of chromosomal, metabolic disorder, and toxic may cause mental retardation. Fragile X Syndrome is most common inherited form of mental retardation. These syndrome have defect in the X-chromosome; mutation in 5'end of the gene with amplification of a CGG repeat ( 200 or more copies). Children with Fragile X Syndrome have long face, enlarged ears and macro-orchidism.

Prader-Willi syndrome, Angelman's syndrome and Rett's syndrome are abnormalities of chromosomal that cause mental retardation.

DEVELOPMENTAL DELAY
The definition of developmental delay is the failure to acquire age appropriate cognitive, language, fine or gross motor skills or social skills. It is not synonymous with mental retardation. To help establish the diagnosis, we can use a standar test- The Denver Developmental Assesment. The causes of developmental delay are similar to those responsible for mental retardation. Treatment for both mental retardation and developmental delay includes referral to early intervention programs for special education and training. (the doc rend-sand)