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MED12-Related Disorders.


Lyons MJ.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2015.
2008 Jun 23 [updated 2013 Jun 06].



The phenotypic spectrum of MED12-related disorders, which is still being defined, includes at a minimum the phenotypes of FG syndrome type 1 (FGS1) and Lujan syndrome (LS). FGS1 and LS share the clinical findings of cognitive impairment, hypotonia, and abnormalities of the corpus callosum. FGS1 is further characterized by absolute or relative macrocephaly, tall forehead, downslanted palpebral fissures, small and simple ears, constipation and/or anal anomalies, broad thumbs and halluces, and characteristic behavior. LS is further characterized by large head, tall thin body habitus, long thin face, high nasal root, high narrow palate, and short philtrum. Carrier females in families with FGS1 and LS are typically unaffected.


The diagnosis of MED12-related disorders relies on molecular genetic testing for common MED12 mutations by sequence analysis of select exons or targeted mutation analysis, followed by sequence analysis of the entire gene as indicated.


Treatment of manifestations: Early individualized education; physical therapy, occupational therapy, and speech therapy for developmental delays; routine management of behavior problems, seizures, strabismus and other ocular anomalies, congenital heart defects, chronic constipation, and imperforate anus. Surveillance: Routine follow-up of growth, psychomotor development, and behavior; routine attention to gastrointestinal functioning and neurologic findings; annual eye examination.


MED12-related disorders are inherited in an X-linked manner. If the mother of a proband has a disease-causing mutation, the chance of transmitting it in each pregnancy is 50%. Males who inherit the mutation will be affected; females who inherit the mutation will be carriers and will usually not be affected. No male with a MED12-related disorder has reproduced. Carrier testing for at-risk female relatives and prenatal testing for pregnancies at increased risk are possible if the disease-causing mutation in the family has been identified.

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