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Knobloch syndrome - a rare collagenopathy, revealing peripheral avascular retina
Puja Maitra1, Parag K Shah1, Prema S1
1Department of Pediatric Retina and Ocular Oncology, Aravind Eye Hospital, Coimbatore, India.
Insights
Genetic testing identified a COL18A1 mutation, confirming Knobloch syndrome in a 5-month-old with retinal detachment. This highlights the importance of genetic testing for pediatric retinal detachments and associated syndromes.
Area of Science:
- Ophthalmology
- Genetics
- Pediatrics
Background:
- Pediatric rhegmatogenous retinal detachments can be associated with genetic syndromes.
- Early-onset retinal detachments warrant investigation for underlying syndromic causes.
Purpose of the Study:
- To investigate the genetic basis of a pediatric rhegmatogenous retinal detachment.
- To identify syndromic associations in a case of early-onset retinal detachment.
Main Methods:
- Clinical examination of a 5-month-old infant with high myopia and retinal detachment.
- Ophthalmic imaging including fluorescein angiography.
- Magnetic Resonance Imaging (MRI) and genetic testing for syndromic associations.
Main Results:
- Genetic testing revealed a pathogenic mutation in COL18A1, indicative of Knobloch syndrome.
- The infant and both parents were carriers of the COL18A1 mutation.
- Peripheral avascular zones were noted in both eyes, a unique finding in this case.
Conclusions:
- Knobloch syndrome should be considered in pediatric retinal detachments with specific clinical features.
- The presence of peripheral avascular zones may be linked to COL18A1 mutations or other factors.
- Genetic testing is crucial for diagnosing syndromic associations in pediatric retinal detachments.
Introduction:
Pediatric rhegmatogenous retinal detachments, especially those presenting at birth or soon afterward, have a high likelihood of syndromic associations that can be confirmed by genetic testing.
Materials And Methods:
A 5-month-old child was found to have high myopia in the right eye (RE) with highly tessellated fundus, opalescent vitreous, and peripheral thinning. Left eye had a shallow retinal detachment for which he underwent belt buckling. The baby had an occipital skin tag. A provisional diagnosis of Stickler syndrome was made.
Results:
On 1-month follow-up, left eye retina was attached and 360° laser barrage was done. Fluorescein angiography was done which revealed peripheral avascular retina in both eyes. MRI and genetic testing were suggestive of syndromic association. Genetic testing revealed pathogenic mutation in COL 18A1 suggestive of Knobloch syndrome in the baby, and both parents were found to be carriers of the same mutation. However, brain MRI showed features not pathognomonic of Knobloch syndrome.
Conclusion:
Although Knobloch syndrome is associated with vitreoretinal degeneration and high risk of retinal detachment, there seems to be no recommendation for prophylaxis in the other eye and therefore we preferred to observe the RE closely. A unique feature noted in our case was the peripheral avascular zone (PAZ). The PAZ could be contributed by multiple factors such as high myopia, or due to endostatin deficiency (which is a derivative of collagen XVIII) or an underlying WNT signalling abnormality.
