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SOX2 anophthalmia syndrome

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Description

SOX2 anophthalmia syndrome is a rare disorder characterized by abnormal development of the eyes and other parts of the body.

People with SOX2 anophthalmia syndrome are usually born without eyeballs (anophthalmia), although some individuals have small eyes (microphthalmia). The term anophthalmia is often used interchangeably with severe microphthalmia because individuals with no visible eyeballs typically have some remaining eye tissue. These eye problems can cause significant vision loss. While both eyes are usually affected in SOX2 anophthalmia syndrome, one eye may be more affected than the other.

Individuals with SOX2 anophthalmia syndrome may also have seizures, brain abnormalities, slow growth, delayed development of motor skills (such as walking), and mild to severe learning disabilities. Some people with this condition are born with a blocked esophagus (esophageal atresia), which is often accompanied by an abnormal connection between the esophagus and the trachea (tracheoesophageal fistula). Genital abnormalities have been described in affected individuals, especially males. Male genital abnormalities include undescended testes (cryptorchidism) and an unusually small penis (micropenis).

Frequency

SOX2 anophthalmia syndrome is estimated to affect 1 in 250,000 individuals. About 10 percent to 15 percent of people with anophthalmia in both eyes have SOX2 anophthalmia syndrome.

Causes

Mutations in the SOX2 gene cause SOX2 anophthalmia syndrome. This gene provides instructions for making a protein that plays a critical role in the formation of many different tissues and organs during embryonic development. The SOX2 protein regulates the activity of other genes, especially those that are important for normal development of the eyes.

Mutations in the SOX2 gene prevent the production of functional SOX2 protein. The absence of this protein disrupts the activity of genes that are essential for the development of the eyes and other parts of the body. Abnormal development of these structures causes the signs and symptoms of SOX2 anophthalmia syndrome.

Inheritance

SOX2 anophthalmia syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Most cases result from new mutations in the SOX2 gene and occur in people with no history of the disorder in their family. In a small number of cases, people with SOX2 anophthalmia syndrome have inherited the altered gene from an unaffected parent who has a SOX2 mutation only in their sperm or egg cells. This phenomenon is called germline mosaicism.

Other Names for This Condition

  • AEG syndrome
  • Anophthalmia-esophageal-genital syndrome
  • SOX2-related eye disorders
  • syndromic microphthalmia 3

Additional Information & Resources

Genetic and Rare Diseases Information Center

Research Studies from ClinicalTrials.gov

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed

References

  • Bakrania P, Robinson DO, Bunyan DJ, Salt A, Martin A, Crolla JA, Wyatt A, Fielder A, Ainsworth J, Moore A, Read S, Uddin J, Laws D, Pascuel-Salcedo D, Ayuso C, Allen L, Collin JR, Ragge NK. SOX2 anophthalmia syndrome: 12 new cases demonstrating broader phenotype and high frequency of large gene deletions. Br J Ophthalmol. 2007 Nov;91(11):1471-6. Epub 2007 May 23. Citation on PubMed or Free article on PubMed Central
  • Kelberman D, de Castro SC, Huang S, Crolla JA, Palmer R, Gregory JW, Taylor D, Cavallo L, Faienza MF, Fischetto R, Achermann JC, Martinez-Barbera JP, Rizzoti K, Lovell-Badge R, Robinson IC, Gerrelli D, Dattani MT. SOX2 plays a critical role in the pituitary, forebrain, and eye during human embryonic development. J Clin Endocrinol Metab. 2008 May;93(5):1865-73. doi: 10.1210/jc.2007-2337. Epub 2008 Feb 19. Citation on PubMed or Free article on PubMed Central
  • Schneider A, Bardakjian TM, Zhou J, Hughes N, Keep R, Dorsainville D, Kherani F, Katowitz J, Schimmenti LA, Hummel M, Fitzpatrick DR, Young TL. Familial recurrence of SOX2 anophthalmia syndrome: phenotypically normal mother with two affected daughters. Am J Med Genet A. 2008 Nov 1;146A(21):2794-8. doi: 10.1002/ajmg.a.32384. Citation on PubMed or Free article on PubMed Central
  • Tziaferi V, Kelberman D, Dattani MT. The role of SOX2 in hypogonadotropic hypogonadism. Sex Dev. 2008;2(4-5):194-9. doi: 10.1159/000152035. Epub 2008 Nov 5. Review. Citation on PubMed
  • Verma AS, Fitzpatrick DR. Anophthalmia and microphthalmia. Orphanet J Rare Dis. 2007 Nov 26;2:47. Review. Citation on PubMed or Free article on PubMed Central
  • Williamson KA, Hever AM, Rainger J, Rogers RC, Magee A, Fiedler Z, Keng WT, Sharkey FH, McGill N, Hill CJ, Schneider A, Messina M, Turnpenny PD, Fantes JA, van Heyningen V, FitzPatrick DR. Mutations in SOX2 cause anophthalmia-esophageal-genital (AEG) syndrome. Hum Mol Genet. 2006 May 1;15(9):1413-22. Epub 2006 Mar 16. Erratum in: Hum Mol Genet. 2006 Jun 15;15(12):2030. Citation on PubMed
  • Williamson KA, Yates TM, FitzPatrick DR. SOX2 Disorder. 2006 Feb 23 [updated 2020 Jul 30]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1300/ Citation on PubMed
  • Zhou J, Kherani F, Bardakjian TM, Katowitz J, Hughes N, Schimmenti LA, Schneider A, Young TL. Identification of novel mutations and sequence variants in the SOX2 and CHX10 genes in patients with anophthalmia/microphthalmia. Mol Vis. 2008 Mar 24;14:583-92. Citation on PubMed or Free article on PubMed Central
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