CXN

Cataracts, Congenital, X-Linked

Clinical Characteristics
Ocular Features: 

The unique status of this type of X-linked cataract is uncertain as the phenotype is highly variable.  It is listed separately in this database because some patients do not have the dysmorphic features of Nance-Horan syndrome (302350) which also is caused by mutations in the NHS gene.  Lens opacities in males usually occur in the nucleus which may cause severe visual impairment.  Heterozygous females have granular opacities along the Y sutures but these may also be seen in males.  Microcornea, variable microphthalmia, and congenital glaucoma (usually secondary) have been noted in a few patients.  

Systemic Features: 

Facial dysmorphology, intellectual impairment, and dental anomalies are often found in patients with X-linked cataracts as part of the Nance-Horan syndrome (302350).  However, these signs may not always be apparent and therefore were not reported in early publications which adds uncertainty to the classification.  That said it is also true that some families in which X-linked cataracts segregate do not have the systemic features in spite of detailed examinations even though they have mutations in NHS. 

Genetics

A mutation in the NHS gene (Xp22.13) can be responsible for X-linked cataracts.   Mutations in the same gene cause Nance-Horan syndrome (302350).  Individuals with typical X-linked cataracts, however, may or may not have systemic malformations. 

A variety of alterations in the NHS gene, including copy number variations, intragenic deletions, and duplication/triplication arrangements, have been found and are likely responsible for the clinical heterogeneity and current nosological confusion.  Until additional fine genotyping is available for more patients it is not possible to determine if a category of X-linked cataracts without NHS mutations exists. 

Pedigree: 
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

Visually significant cataracts must be removed early to allow normal visual development.  Secondary glaucoma and retinal detachments are post-operative risks. 

References
Article Title: 

X-linked cataract and Nance-Horan syndrome are allelic disorders

Coccia M, Brooks SP, Webb TR, Christodoulou K, Wozniak IO, Murday V, Balicki M, Yee HA, Wangensteen T, Riise R, Saggar AK, Park SM, Kanuga N, Francis PJ, Maher ER, Moore AT, Russell-Eggitt IM, Hardcastle AJ. X-linked cataract and Nance-Horan syndrome are allelic disorders. Hum Mol Genet. 2009 Jul 15;18(14):2643-55.

PubMed ID: 
19414485
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