February 2012
Volume 53, Issue 2
Free
Letters to the Editor  |   February 2012
Corneal Thinning Phenotypes—An Alternative Perspective
Author Affiliations & Notes
  • Osama Giasin
    Calderdale Royal Hospital, Halifax, United Kingdom;
  • Rehna S. Khan
    the Calderdale Royal Infirmary, Halifax, United Kingdom; and
  • Kamron Khan
    the Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds, United Kingdom.
Investigative Ophthalmology & Visual Science February 2012, Vol.53, 1048. doi:10.1167/iovs.11-9372
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      Osama Giasin, Rehna S. Khan, Kamron Khan; Corneal Thinning Phenotypes—An Alternative Perspective. Invest. Ophthalmol. Vis. Sci. 2012;53(2):1048. doi: 10.1167/iovs.11-9372.

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      © ARVO (1962-2015); The Authors (2016-present)

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We were very interested to read of a second mutation in the seed region of miR-184 resulting in EDICT syndrome. 1 We were unsure after reading the paper, however, of how the corneal findings should be classified and of the statement that the family “does not demonstrate a keratoconus phenotype.” Keratoconus, the commonest disorder of corneal thinning and steepening, has been linked with VSX1 and SOD1 in single studies and up to 14 different genetic loci. 2 It has a variable phenotype, and while few would dispute the diagnosis in classic cases with central corneal thinning, identifying variants such as forme fruste disease (where a cone may not be present) may be more challenging. A less common disorder of corneal thinning is keratoglobus, in which the thinning is global and often most pronounced in the periphery. Iris hypoplasia with keratoglobus has been described. 3 Similarly, the occurrence of keratoglobus with a corneal endothelial disease, posterior polymorphous corneal dystrophy, has also been recognized. 4  
Histopathologic studies of advanced keratoconus are very similar to those of keratoglobus. 5 Biochemical analyses also reveal that a decreased expression of α1 proteinase inhibitor and upregulation of transcription factor Sp1 are common to both. 5 Disorders of retinal development (as found in 4 of 10 EDICT patients) can also co-segregate with corneal ectasia; CRB1 mutations causing Leber congenital amaurosis (LCA) have been associated with both keratoconus and keratoglobus. 6  
We wonder if the reported corneal phenotype in EDICT syndrome should fall within the keratoconus/-globus spectrum and, as such, should be considered a candidate gene for these as well as other “cornea plus” syndromes? 
References
Iliff BW Riazuddin SA Gottsch JD . A single-base substitution in the seed region of miR-184 causes EDICT syndrome. Invest Ophthalmol Vis Sci. 2012;53:348–353. [CrossRef] [PubMed]
Nowak DM Gajecka M . The genetics of keratoconus. Middle East Afr J Ophthalmol. 2011;18:2–6. [CrossRef] [PubMed]
Sidorov EG Pivovarov NN . Dysgenesis of the iris and anterior chamber angle associated with keratoglobus (in Russian). Vestn Oftalmol. 1975;Nov–Dec(6);76.
Harissi-Dagher M Dana MR Jurkunas UV . Keratoglobus in association with posterior polymorphous dystrophy. Cornea. 2007;26:1288–1291. [CrossRef] [PubMed]
Meghpara B Nakamura H Vemuganti GK . Histopathologic and immunohistochemical studies of keratoglobus. Arch Ophthalmol. 2009;127:1029–1035. [CrossRef] [PubMed]
McMahon TT Kim LS Fishman GA . CRB1 gene mutations are associated with keratoconus in patients with Leber congenital amaurosis. Invest Ophthalmol Vis Sci. 2009;50:3185–3187. [CrossRef] [PubMed]
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