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Fragile X syndrome (FXS) is the most common cause of inherited intellectual disabilities and autism spectrum disorders, and it is an X-linked disorder in which there is a deficiency of the fragile X mental retardation 1 protein. This protein is crucial in regulating translation of mRNAs related to dendritic maturation and cognitive development. The phenotype of FXS is characterized by neurobehavioral alterations, social deficits, communication difficulties, and findings which suggest an alteration of connective tissue, especially in the ligaments and muscles, cardiovascular system and genitourinary system. Connective tissue connects and supports all other tissues of the body and is composed of cells and extracellular matrix (ECM). Several proteins have been involved in the connective tissue abnormalities associated with the FXS, such as matrix metalloproteinase 9, which plays an important role in the homeostasis of the ECM, being a potential therapeutic target for certain tetracycline antibiotics that have shown beneficial effects in FXS. Here, we review connective tissue problems described in FXS., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Fragile X Syndrome (FXS) is a genetic disease due to a CGG trinucleotide expansion, named full mutation (greater than 200 CGG repeats), in the fragile X mental retardation 1 gene locus Xq27.3; which leads to an hypermethylated region in the gene promoter therefore silencing it and lowering the expression levels of the fragile X mental retardation 1, a protein involved in synaptic plasticity and maturation. Individuals with FXS present with intellectual disability, autism, hyperactivity, long face, large or prominent ears and macroorchidism at puberty and thereafter. Most of the young children with FXS will present with language delay, sensory hyper arousal and anxiety. Girls are less affected than boys, only 25% have intellectual disability. Given the genomic features of the syndrome, there are patients with a number of triplet repeats between 55 and 200, known as premutation carriers. Most carriers have a normal IQ but some have developmental problems. The diagnosis of FXS has evolved from karyotype with special culture medium, to molecular techniques that are more sensitive and specific including PCR and Southern Blot. During the last decade, the advances in the knowledge of FXS, has led to the development of investigations on pharmaceutical management or targeted treatments for FXS. Minocycline and sertraline have shown efficacy in children.