Familial mental retardation (FMR) is defined as form of mental retardation that does not involve biological damage, but instead represents the low end of the normal distribution of intelligence.

Familial mental retardation is a term used to describe a group of genetic disorders that cause intellectual disability (ID) or cognitive impairment. These disorders are caused by mutations or alterations in genes that are inherited from parents.

FMR can be caused by a number of different genetic mutations, including fragile X syndrome, which is the most common inherited cause of ID. Other examples of FMR include Down syndrome, Rett syndrome, and Angelman syndrome.

Individuals with FMR may have a range of symptoms, including developmental delays, problems with communication, difficulty learning new skills, and social and emotional issues. Treatment for FMR typically involves a multidisciplinary approach, including special education services, speech and language therapy, occupational therapy, and behavioral therapy.

It is important to note that FMR is different from acquired intellectual disability, which can be caused by factors such as brain injury, infections, or exposure to toxins.