© 2018, GENASSIST, Inc.
By Keith S. Wexler, MBA, CFO, Business Development Director GENASSIST, Inc.
Paul Wexler, M.D., F.A.C.O.G., Medical Director, GENASSIST, Inc.
Clinical Professor, Department of OB/GYN, University of Colorado Health Sciences Center
Clinical Professor, Division of Genetics/Dept. of Pediatrics, Univ. of Colorado/The Children’s Hospital
FG Syndrome Type 3 (diagnosed by Dr. Opitz) is characterized by:
- Developmental delay
- Reduced muscle tone and anal abnormalities
At least 45 other symptoms are often present and include:
- Extroverted personality
- Tethered spinal cord
- Cleft larynx
- Possible absence of corpus callosum
- Relative macrocephaly
- Easy frustration
- Unusual hair whorls
FG Syndrome Type 3 is inherited in an X-linked recessive manner affecting almost exclusively males. Approximately 5 regions on the X chromosome have been identified linked to the FG Syndrome.
The MED12 gene is the most common cause for the FG Syndrome. The FLNA (FGS2), CASK (FGS4), UPF3B (FGS6) and BRWD3 (FGS7) genes all on the X chromosome and have been found in children with the FG Syndrome. The causative mutation(s) for Type 3 has not been definitely identified.
Rarely the same disorder or a similar disorder (phenocopy) can result from a different cause. Most tests using DNA extracted from the blood of an individual analyze the most common variations (mutations) known to be responsible for a particular disorder (disease).
Evaluation of these variations (mutations) will Not detect all carriers of the disorder and are not designed to detect other disorders that may be similar to the disorder being studied. Depending on the disorder being studied, detection rates may vary considerably from as low as 40-60% to as high as 90-98%.
Therefore, when there is a high degree of suspicion for a disorder or following negative testing, symptoms suggest that the disorder may be present, additional testing or more definitive testing should be used if available.
The accuracy for detection of a specific disorder should continue to improve as additional deleterious mutations are identified.