X-linked infantile nystagmus is a condition characterized by abnormal eye movements. Nystagmus is a term that refers to involuntary side-to-side movements of the eyes. In people with this condition, nystagmus is present at birth or develops within the first six months of life. The abnormal eye movements may worsen when an affected person is feeling anxious or tries to stare directly at an object. The severity of nystagmus varies, even among affected individuals within the same family. Sometimes, affected individuals will turn or tilt their head to compensate for the irregular eye movements.
The incidence of all forms of infantile nystagmus is estimated to be 1 in 5,000 newborns; however, the precise incidence of X-linked infantile nystagmus is unknown.
Mutations in the FRMD7 gene cause X-linked infantile nystagmus. The FRMD7 gene provides instructions for making a protein whose exact function is unknown. This protein is found mostly in areas of the brain that control eye movement and in the light-sensitive tissue at the back of the eye (retina). Research suggests that FRMD7 gene mutations cause nystagmus by disrupting the development of certain nerve cells in the brain and retina.
In some people with X-linked infantile nystagmus, no mutation in the FRMD7 gene has been found. The genetic cause of the disorder is unknown in these individuals. Researchers believe that mutations in at least one other gene, which has not been identified, can cause this disorder.
This condition is inherited in an X-linked pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two copies of the X chromosome), one altered copy of the gene in each cell can cause the condition, although affected females may experience less severe symptoms than affected males. Approximately half of the females with only one altered copy of the FRMD7 gene in each cell have no symptoms of this condition.
Other Names for This Condition
- congenital motor nystagmus
- FRMD7-related infantile nystagmus
- idiopathic infantile nystagmus
- X-linked congenital nystagmus
- X-linked idiopathic infantile nystagmus
Additional Information & Resources
Genetic Testing Information
Genetic and Rare Diseases Information Center
Research Studies from ClinicalTrials.gov
Catalog of Genes and Diseases from OMIM
Scientific Articles on PubMed
- He X, Gu F, Wang Z, Wang C, Tong Y, Wang Y, Yang J, Liu W, Zhang M, Ma X. A novel frameshift mutation in FRMD7 causing X-linked idiopathic congenital nystagmus. Genet Test. 2008 Dec;12(4):607-13. doi: 10.1089/gte.2008.0070. Citation on PubMed
- Li N, Wang L, Cui L, Zhang L, Dai S, Li H, Chen X, Zhu L, Hejtmancik JF, Zhao K. Five novel mutations of the FRMD7 gene in Chinese families with X-linked infantile nystagmus. Mol Vis. 2008 Apr 18;14:733-8. Citation on PubMed or Free article on PubMed Central
- Sarvananthan N, Surendran M, Roberts EO, Jain S, Thomas S, Shah N, Proudlock FA, Thompson JR, McLean RJ, Degg C, Woodruff G, Gottlob I. The prevalence of nystagmus: the Leicestershire nystagmus survey. Invest Ophthalmol Vis Sci. 2009 Nov;50(11):5201-6. doi: 10.1167/iovs.09-3486. Epub 2009 May 20. Citation on PubMed
- Self J, Lotery A. A review of the molecular genetics of congenital Idiopathic Nystagmus (CIN). Ophthalmic Genet. 2007 Dec;28(4):187-91. Review. Citation on PubMed
- Self JE, Shawkat F, Malpas CT, Thomas NS, Harris CM, Hodgkins PR, Chen X, Trump D, Lotery AJ. Allelic variation of the FRMD7 gene in congenital idiopathic nystagmus. Arch Ophthalmol. 2007 Sep;125(9):1255-63. Citation on PubMed
- Shiels A, Bennett TM, Prince JB, Tychsen L. X-linked idiopathic infantile nystagmus associated with a missense mutation in FRMD7. Mol Vis. 2007 Nov 29;13:2233-41. Citation on PubMed
- Tarpey P, Thomas S, Sarvananthan N, Mallya U, Lisgo S, Talbot CJ, Roberts EO, Awan M, Surendran M, McLean RJ, Reinecke RD, Langmann A, Lindner S, Koch M, Jain S, Woodruff G, Gale RP, Bastawrous A, Degg C, Droutsas K, Asproudis I, Zubcov AA, Pieh C, Veal CD, Machado RD, Backhouse OC, Baumber L, Constantinescu CS, Brodsky MC, Hunter DG, Hertle RW, Read RJ, Edkins S, O'Meara S, Parker A, Stevens C, Teague J, Wooster R, Futreal PA, Trembath RC, Stratton MR, Raymond FL, Gottlob I. Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus. Nat Genet. 2006 Nov;38(11):1242-4. Epub 2006 Oct 1. Erratum in: Nat Genet. 2011 Jul;43(7):720. Bastawrous, Andrew [added]. Citation on PubMed or Free article on PubMed Central
- Thomas MG, Maconachie G, Hisaund M, Gottlob I. FRMD7-Related Infantile Nystagmus. 2009 Feb 12 [updated 2018 Aug 16]. 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/NBK3822/ Citation on PubMed
- Thomas S, Proudlock FA, Sarvananthan N, Roberts EO, Awan M, McLean R, Surendran M, Kumar AS, Farooq SJ, Degg C, Gale RP, Reinecke RD, Woodruff G, Langmann A, Lindner S, Jain S, Tarpey P, Raymond FL, Gottlob I. Phenotypical characteristics of idiopathic infantile nystagmus with and without mutations in FRMD7. Brain. 2008 May;131(Pt 5):1259-67. doi: 10.1093/brain/awn046. Epub 2008 Mar 27. Citation on PubMed
- Zhang B, Liu Z, Zhao G, Xie X, Yin X, Hu Z, Xu S, Li Q, Song F, Tian J, Luo W, Ding M, Yin J, Xia K, Xia J. Novel mutations of the FRMD7 gene in X-linked congenital motor nystagmus. Mol Vis. 2007 Sep 13;13:1674-9. Citation on PubMed
- Zhang Q, Xiao X, Li S, Guo X. FRMD7 mutations in Chinese families with X-linked congenital motor nystagmus. Mol Vis. 2007 Aug 3;13:1375-8. Citation on PubMed