1800 800 340

Disability Glossary

Search for glossary terms (regular expression allowed)
Begin with Contains Exact termSounds like
Term Definition
Fragile X syndrome

Fragile X syndrome (FXS), Martin–Bell syndrome, or Escalante's syndrome (more commonly used in South American countries), a genetic syndrome, is the most commonly known single-gene cause of autism and the most common inherited cause of intellectual disability.[1][2] It results in a spectrum of characteristic physical and intellectual limitations and emotional and behavioral features which range from severe to mild in manifestation.

The syndrome is associated with the expansion of a single trinucleotide gene sequence (CGG) on the X-chromosome, and results in a failure to express the protein coded by the FMR1 gene, which is required for normal neural development. There are four generally accepted states of the chromosome region involved in Fragile X syndrome which relate to the length of the repeated CGG sequence; Normal (29–31 CGG repeats) (not affected by the syndrome), Premutation (55–200 CGG repeats)(not affected by the syndrome), Full Mutation (more than 200 CGG repeats)(affected), and Intermediate or Gray Zone Alleles (40–60 repeats).

J. Purdon Martin and Julia Bell in 1943, described a pedigree of X-linked mental disability, without considering the macroorchidism (larger testicles). In 1969 Herbert Lubs first sighted an unusual "marker X chromosome" in association with mental disability.

Friedreich's ataxia

Friedreich's ataxia is an inherited disease that causes progressive damage to the nervous system, resulting in symptoms ranging from gait disturbance to speech problems; it can also lead to heart disease and diabetes.

The ataxia of Friedreich's ataxia results from the degeneration of nerve tissue in the spinal cord, in particular sensory neurons essential (through connections with the cerebellum) for directing muscle movement of the arms and legs. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath (the insulating covering on some nerve cells that helps conduct nerve impulses).