Fragile X in the Family

Discussion Fragile X syndrome (FXS) was first clinically described in 1943 by Martin-Bell and in 1969 Lubs found a fragility at the terminal end of the X chromosome. In 1991, three different research groups independently cloned the mutation for the FMR1 gene (Fragile X mental retardation type 1) which has a CGG triplet expansion. The FMR1 gene codes for the FMR protein which is a major regulator of synaptic plasticity and is expressed in the brain and spermatogonia mainly but many other tissues during fetal and early neonatal development. The number of triplets and methylation correlates with clinical expression (increased numbers have increased clinical expression). It is an X-linked dominant gene with reduced penetrance. Overall it has an incidence of 1:4000 for males and 1:7000 in females. Learning Point FXS occurs from inactivation of the FMR1 gene. FXS is the most common cause of inherited intellectual disability. It is also a leading form of autism spectrum disorders. Patients may also have seizures, abnormal head movements, hyperactive behavior, and poor eye contact. FXS is suspected in patients with developmental delays and is diagnosed by polymerase chain reaction which can determine the number of CGG repeats as well as other genetic information that is important for genetic counseling. The number of repeats tends to increase in subsequent generations especially with repeats in the permutation zone. People with 6-44 repeats are considered normal. People with 45-54...
Source: PediatricEducation.org - Category: Pediatrics Authors: Tags: Uncategorized Source Type: news