Causes of Mental Retardation/

Developmental Cognitive Disability  

 

I. Introduction:

 

There are hundreds of known causes of MR.

 

Yet, many cases are of unknown causation.

 

II. Onset before birth:

 

A. Chromosomal Abnormalities (normal chromosome image link)

 

      1. Down Syndrome

          A. Trisomy 21

          B. Translocation

          C. Mosaicism

          D. Characteristics of DS

      2. Other Trisomies
      Patau's Syndrome (Trisomy 13) and Edward's Syndrome (Trisomy 18)

 

      3. Prader-Willi Syndrome (Victor's Story)

 

      4. Fragile X Syndrome

    

B. Syndromes that result from defective genes

 

      1. Metabolic Disorders (faulty enzyme production)

          

           A. Phenylketonuria (PKU)

           B. Tay-Sachs (pictures)

           C. Hurler Syndrome

           D. Lesch-Nyhan Syndrome (Picture from Wickipedia)

 

      2. Endocrine (hormonal) Disorders such as Hypothyroidism (“Cretinism”)

          

 

      3. Cranial Abnormalities (Microcephaly)

 

C. Maternal Drug Use Such as Fetal Alcohol Syndrome see FAS brain image)

 

D. Maternal Infection (Such as Rubella)

 

III. Onset at birth:

 

A. Perinatal Anoxia

 

B. Mechanical Injury

 

 

IV. Onset after birth:

 

A. Infection

     1. Meningitis

     2. Encephalitis

 

B. Head Injuries

     1. Car Accidents

     2. Shaken-baby Syndrome

 

C. Toxicity (Such as lead poisoning)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Down Syndrome

(Characteristics)

 

1. Lowered Intellectual Functioning

    (Often Moderate Mental Retardation)

 

2. Small, Flat Skull

 

3. Short, Broad Neck

 

4. Large, Fissured Tongue

 

5. Speech Disorders & Coarse, Low Voice

 

6. Sparse, Fine, Straight Hair

 

7. Short, Flat Hands With Single Crease

 

8. Poor Muscle Tone

 

9. Short, Stocky Build

 

10. Prone to Congenital Heart Defects

 

11. Sunny Disposition!