Compound heterozygosity at the FMR1 gene

Area of Science:

• Genetics
• Molecular Biology
• Human Disease

Background:

• Fragile X syndrome is a genetic disorder caused by an excessive number of CGG repeats in the FMR1 gene.
• Full mutations (≥200 repeats) cause the syndrome, while premutations (50-200 repeats) are typically associated with unaffected carriers.

Observation:

• This study reports a rare case of a compound heterozygous female with Fragile X syndrome.
• She carries CGG repeats in the FMR1 gene spanning both premutation and full mutation ranges.

Findings:

• The premutation range repeats were inherited from her father.
• The full mutation range repeats represent an expansion of the premutation inherited from her mother.

Implications:

• The proband's offspring face a significant risk of inheriting Fragile X syndrome.
• Genetic counseling is recommended for the proband's paternal uncle and cousins due to potential risk.