| Knobloch syndrome | |
|---|---|
| Other names | Myopia retinal detachment encephalocele[1] |
Knobloch syndrome is a raregenetic disorder presenting severeeyesight problems and often a defect in theskull. It was named after the ophthalmologist William Hunter Knobloch (1926–2005),[2] who first described the syndrome in 1971.[3] A usual occurrence is adegeneration of thevitreous humour and theretina, two components of theeye. This breakdown often results in the separation of the retina (the light-sensitive tissue at the back of the eye) from the eye, calledretinal detachment, which can be recurrent.[4] Extrememyopia (near-sightedness) is a common feature.[4] The limited evidence available fromelectroretinography suggests that acone-rod pattern of dysfunction is also a feature.[5]
Knobloch syndrome is caused bymutations in anautosomal recessive inheritedgene. These mutations have been found in theCOL18A1 gene that instructs for the formation of aprotein that buildscollagen XVIII. This type of collagen is found in thebasement membranes of various body tissues. Its deficiency in the eye is thought to be responsible for affecting normal eye development.[4] There are two types of Knobloch syndrome and the case has been made for a third.[6]When caused by mutations in the COL18A1 gene it is called Knobloch syndrome type 1.[7] The genes causing types II and III have yet to be identified.[citation needed]
Knobloch syndrome is also characterised bycataracts, dislocated lens with skull defects such asoccipitalencephalocele and occipitalaplasia.[8] Encephalocele is aneural tube defect where the skull has not completely closed and sac-like protrusions of the brain can push through the skull; (it can also result from other causes).[9]In Knobloch's syndrome this is usually seen in the occipital region, and aplasia is the underdevelopment of tissue again in this reference in the occipital area.[citation needed]
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