CGG repeats refer to a specific sequence of DNA where the nucleotides cytosine (C) and guanine (G) are repeated multiple times. This trinucleotide repeat is particularly significant in the context of genetic disorders. In the field of gynecology, these repeats are most commonly associated with Fragile X Syndrome and Premature Ovarian Insufficiency (POI).
Fragile X Syndrome (FXS) is a genetic condition that results from the expansion of CGG repeats within the FMR1 gene located on the X chromosome. Normally, this gene contains 5-44 CGG repeats. When the number of repeats increases to a range between 55 and 200, it is called a premutation. If the number exceeds 200, it is considered a full mutation and leads to Fragile X Syndrome, which can cause intellectual disabilities, behavioral challenges, and various physical features.
Women who carry the premutation of the FMR1 gene (55-200 CGG repeats) are at an increased risk of developing Premature Ovarian Insufficiency (POI), which is characterized by the loss of normal ovarian function before the age of 40. POI can lead to infertility, irregular menstrual cycles, and early menopause. It is estimated that approximately 20% of women with a premutation will develop POI.
Testing for CGG repeats usually involves a simple blood test. The DNA is extracted from the blood sample and analyzed using techniques such as Polymerase Chain Reaction (PCR) or Southern blotting. These methods allow for the determination of the number of CGG repeats in the FMR1 gene, helping to diagnose conditions like Fragile X Syndrome or assess the risk of developing POI.
CGG repeat testing is particularly recommended for women who have a family history of Fragile X Syndrome or POI. It is also advised for women experiencing unexplained infertility or early signs of menopause. Genetic counseling is often recommended before and after testing to help individuals understand the implications of the results.
A positive test result indicating a premutation or full mutation can have various implications. For women with a premutation, there is an increased risk of developing POI and passing the expanded CGG repeats to their offspring, potentially resulting in Fragile X Syndrome. It is crucial for individuals with a positive result to seek genetic counseling for further guidance on family planning and management of potential health issues.
Currently, there is no cure for Fragile X Syndrome or Premature Ovarian Insufficiency. However, early intervention and supportive therapies can significantly improve the quality of life for affected individuals. For women with POI, hormone replacement therapy may be an option to manage symptoms. In the case of infertility, assisted reproductive technologies such as In Vitro Fertilization (IVF) may be considered.
