Some Chromosomal and Genetic Causes of Intellectual Disability*

Chromosomal abnormalities

5p- syndrome (5p minus syndrome or cri du chat syndrome)

Down syndrome

Klinefelter syndrome

Mosaicisms

Trisomy 13 (Patau syndrome)

Trisomy 18 (Edwards syndrome)

Turner syndrome

Genetic metabolic disorders

Autosomal recessive disorders:

• Aminoacidurias and acidemias

• Galactosemia

• Maple syrup urine disease

• Phenylketonuria

• Lysosomal defects

• Gaucher disease

• Hurler syndrome (mucopolysaccharidosis)

• Niemann-Pick disease

• Tay-Sachs disease

• Peroxisomal disorders

X-linked recessive disorders:

• Hunter syndrome (a variant of mucopolysaccharidosis)

• Lesch-Nyhan syndrome (hyperuricemia)

• Oculocerebrorenal syndrome (Lowe syndrome)

Genetic neurologic disorders

Autosomal dominant disorders:

• Myotonic dystrophy

• Neurofibromatosis

• Tuberous sclerosis complex

Autosomal recessive disorders:

• Primary microcephaly

X-linked disorders:

• Fragile X syndrome

• Rett syndrome