Fragile X is the most common inherited cause of intellectual disability and the leading known cause of autism. It results from a gene expansion on the X-chromosome (FMR1) which leads to a decrease in (or absence of) a protein (FMRP) that functions in neurological development and connective tissue formation. Although the disorder is present at birth, most parents don't get a diagnosis of their child with Fragile X until approximately age 2. Exceptions to that would primarily be in children born of a known Fragile X carrier.
Fragile X can manifest itself by a wide variety of symptoms, including developmental delay/disability, ADHD, autistic characteristics, long face, large or prominent ears, hyper-extensible joints, flat feet, macroorchidism (boys), soft and velvety skin, broad forehead and/or a large head, anxiety, aggression, poor eye contact, sensory integration disorder, OCD, difficulty picking up social "cues", speech differences (from stuttering, echolalia, mispronounciation to inability to speak at all) and seizures.
Female carriers of Fragile X may have premature ovarian failure (POF) and otherwise unaffected male and female carriers can develop Fragile X Tremor Ataxia Syndrome (FXTAS) late in life.
Fragile X Syndrome is easily diagnosed by a simple DNA blood test using Southern Blot/PCR analysis.
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