The distinct ophthalmic phenotype of Knobloch syndrome in children
- 1Division of Pediatric Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
- 2Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
- 3Department of Pediatrics, King Khalid University Hospital and College of Medicine, King Saud University, Riyadh, Saudi Arabia
- 4Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
- Correspondence to Dr Arif O Khan, Division of Pediatric Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh 11462, Saudi Arabia;
Contributors All authors listed met the following three criteria: (1) substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; (2) drafting the article or revising it critically for important intellectual content; and (3) final approval of the version to be published.
- Accepted 5 February 2012
- Published Online First 7 March 2012
Background Knobloch syndrome is defined as a triad of occipital defect, high myopia and vitreo-retinal degeneration (often with later retinal detachment); however, the ocular phenotype is not well defined. This report characterises eye findings of the syndrome in children with genetically confirmed disease.
Methods Case series of Saudi children with previously documented homozygous mutations in COL18A1 or ADAMTS18.
Results All eight children (4–15 years old; five families) had smooth (cryptless) irides, high myopia (−10 to −20 dioptres) and distinctive vitreo-retinal degeneration consisting of diffuse very severe retinal pigment epithelium atrophic changes with prominent choroidal vessel show, macular atrophic lesions with or without a ‘punched out’ appearance and white fibrillar vitreous condensations. In two probands and a sibling, this distinctive retinal appearance was the basis for initial clinical diagnosis. Six children had temporal ectopia lentis and four had posterior perinuclear lens opacity. Additional features included developmental delay (two), epilepsy (one) and heterotopic grey matter in the lateral ventricles (one). Four children had no clinically discernible occipital defect.
Conclusion Taken together, smooth iridies, ectopia lentis and characteristic vitreo-retinal degeneration seem pathognomonic. Although it is a defining feature of the syndrome, clinically discernible occipital defect is not a sine qua non for the diagnosis. Ophthalmologists are uniquely able to diagnose Knobloch syndrome.
Funding This study was funded in part by a KACST grant (08-MED497-20) to FSA. The providers of the grant had no role in the conduct, design or interpretation of the research. The authors are responsible for conception and design, acquisition of data, analysis and interpretation of data, drafting the article and revising it critically for important intellectual content, and final approval.
Competing interests None.
Patient consent Obtained.
Ethics approval Approval provided by the King Faisal Specialist Hospital and Research Center and the King Khaled Eye Specialist Hospital institutional review boards.
Provenance and peer review Not commissioned; externally peer reviewed.