3. MentalRetardation PKU is a metabolic disorder, which if untreated leads to mentalretardation. Learn more about the PKU and its effects on PKU.com. www.pku.com/retardation
6. MentalRetardation Information Fragile X syndrome is a hereditary condition which causes a wide range of mental impairment, from mild learning disabilities to severe mentalretardation. Research online. www.fragilex.org