Fragile X syndrome

What is Fragile X syndrome?

Fragile X syndrome is part of a family of genetic disorders caused by a particular gene's pre or full mutation. It affects males more frequently than females, and symptoms are often more severe in males.

Symptoms may vary broadly depending on the number of CGG repeats. They might include variable degrees of developmental delay, especially in males, accompanied by macroorchidism and large ears, to tremor/ataxia in adulthood or premature ovary failure in women.

Fragile X syndrome mostly impacts individuals' intellectual abilities and behavior.

Syndrome Synonyms
Fragile X syndrome Marker X Syndrome Martin-bell Syndrome Mental Retardation, X-linked, Associated With Marxq28 X-linked Mental Retardation And Macroorchidism

What gene changes cause Fragile X syndrome?

Fragile X syndrome occurs due to a full mutation of the FMR1 gene, making a protein necessary for typical brain development. Individuals with Fragile X syndrome do not produce this protein as a result of the mutation.

With syndromes inherited in an X-linked dominant pattern, a mutation in just one of the copies of the gene, causes the syndrome. This can be in one of the female X chromosomes, and in the one X chromosomes males have. Males tend to have more severe symptoms than females.

Genes, locations, and inheritance modes
APP, 21q21.3
FMR1, Xq27.3
AFF2, Xq28

OMIM Number - 300624 (please check the OMIM page for updated information)

What are the main symptoms of Fragile X syndrome?

The main symptoms of Fragile X syndrome may vary between individuals and may also vary in the extent of their severity.

Common symptoms include a long and narrow face, large ears, soft skin, enlarged testicles (macrorchidea) in males, flat feet, an arched palate and very flexible joints.

Mild to moderate intellectual disability and developmental delay is also characteristic of Fragile X syndrome. There are also associations between the syndrome and a higher risk of a diagnosis for autism, ADHD, and other social and sensory-related conditions.

Females with a full mutation of the gene can develop premature ovarian failure as well as tremors/ataxia syndrome in adulthood.

Possible clinical traits/features:
Mitral valve prolapse, Muscular hypotonia, Abnormal head movements, Large forehead, Macrotia, Joint hypermobility, Joint laxity, Macroorchidism, Macroorchidism, postpubertal, Long face, Narrow face, Mandibular prognathia, Pectus excavatum, Neurological speech impairment, Intellectual disability, moderate, Otitis media, Periventricular heterotopia, Poor eye contact, Pes planus, Sinusitis, Seizure, Cognitive impairment, Hyperactivity, Folate-dependent fragile site at Xq28, Cerebral cortical atrophy, Attention deficit hyperactivity disorder, Self-injurious behavior, Autism, Abnormality of the pinna, Abnormal mitral valve morphology, Dilatation of the ascending aorta, Congenital macroorchidism, Coarse facial features, X-linked dominant inheritance, Strabismus, Frontal bossing, Scoliosis, Macrocephaly, Incomplete penetrance

How does someone get tested for Fragile X syndrome?

The initial testing for Fragile X syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow. 

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.   

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