For Physicians. By Physicians.™
For Physicians. By Physicians.™
Fragile X is a serious X-linked dominant genetic disorder that is strongly associated with significant developmental and CNS manifestations. Prevalence approximately 1/4000 males and 1/8000 females.
ACOG
ACMG
Note: Genetic Counseling and informed consent are key components of screening and diagnostic testing
Most cases (98%) caused by expanded trinucleotide repeat (CGG)n in the FMR1 gene
| Maternal Repeat Size | %Full Mutation | #AGG – %Full Mutation |
|---|---|---|
| 45 – 49 | 0% | 0% |
| 50 – 54 | 0 | 0% |
| 55 – 59 | 0.5 | 0 AGG – 3% >1 AGG – 0% |
| 60 – 64 | 1.7 | 0 AGG – 5% >1 AGG – 0% |
| 65 – 69 | 7 | 0 AGG – 17% >1 AGG – 0% |
| 70 – 74 | 21 | 0 AGG – 52% 1 AGG – 7% 2 AGG – 0% |
| 75 – 79 | 47 | 0 AGG – 73% 1 AGG – 33% 2 AGG – 7% |
| 80-84 | 62 | 0 AGG – 87% 1 AGG – 67% 2 AGG – 15% |
| 85 – 89 | 81 | 0 AGG – 88% 1 AGG – 83% 2 AGG – 50% |
| 90 – 99 | 94 | |
| ≥100 – 200 | 98 | |
| >200 | 100 |
Adapted from Nolin et al., 2011 and 2015
Fragile X analysis of 1112 prenatal samples from 1991 to 2010
GeneReviews: FMR1-Related Disorders
ACOG Committee Opinion 691: Carrier Screening for Genetic Conditions
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