Knobloch syndrome

{{Infobox medical condition (new)

| name = Knobloch syndrome

| synonyms = Myopia retinal detachment encephalocele{{cite web |title=Knobloch syndrome {{!}} Genetic and Rare Diseases Information Center (GARD) – an NCATS Program |url=https://rarediseases.info.nih.gov/diseases/380/knobloch-syndrome |website=rarediseases.info.nih.gov |access-date=17 March 2019}}

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Knobloch syndrome is a rare genetic disorder presenting severe eyesight problems and often a defect in the skull. It was named after the ophthalmologist William Hunter Knobloch (1926–2005),Ramsay RC. William H. Knobloch, MD (1926-2005). Obituary. Arch Ophthalmol 2006; 124: 431; https://jamanetwork.com/journals/jamaophthalmology/fullarticle/417580 who first described the syndrome in 1971.Knobloch WH, Layer JM. Retinal detachment and encephalocele. J Pediat Ophthalmol 1971; 8: 181-184 A usual occurrence is a degeneration of the vitreous humour and the retina, two components of the eye. This breakdown often results in the separation of the retina (the light-sensitive tissue at the back of the eye) from the eye, called retinal detachment, which can be recurrent.{{cite web|url=http://ghr.nlm.nih.gov/condition/knobloch-syndrome|title=Knobloch syndrome|first=Genetics Home|last=Reference|website=Genetics Home Reference}} Extreme myopia (near-sightedness) is a common feature. The limited evidence available from electroretinography suggests that a cone-rod pattern of dysfunction is also a feature.{{Cite journal|title=Molecular and Clinical Findings in Patients with Knobloch Syndrome| pmid=27259167 | doi=10.1001/jamaophthalmol.2016.1073 | volume=134| issue=7 | journal=JAMA Ophthalmol| pages=753–62 | last1 = Hull | first1 = S | last2 = Arno | first2 = G | last3 = Ku | first3 = CA | last4 = Ge | first4 = Z | last5 = Waseem | first5 = N | last6 = Chandra | first6 = A | last7 = Webster | first7 = AR | last8 = Robson | first8 = AG | last9 = Michaelides | first9 = M | last10 = Weleber | first10 = RG | last11 = Davagnanam | first11 = I | last12 = Chen | first12 = R | last13 = Holder | first13 = GE | last14 = Pennesi | first14 = ME | last15 = Moore | first15 = AT| year=2016 | url = http://discovery.ucl.ac.uk/1499967/1/Hull%20et%20al%20Molecular%20and%20Clinical%20Findings%20in%20Patients%20With%20Knobloch%20Syndrome%20VoR.pdf | doi-access = free }}

Knobloch syndrome is caused by mutations in an autosomal recessive inherited gene. These mutations have been found in the COL18A1 gene that instructs for the formation of a protein that builds collagen XVIII. This type of collagen is found in the basement membranes of various body tissues. Its deficiency in the eye is thought to be responsible for affecting normal eye development. There are two types of Knobloch syndrome and the case has been made for a third.{{Cite journal|title=Mapping of a novel type III variant of Knobloch syndrome (KNO3) to chromosome 17q11.2| pmid=17975799 | doi=10.1002/ajmg.a.31739 | volume=143A| issue=23 | journal=Am J Med Genet A| pages=2768–74 | last1 = Khaliq | first1 = S | last2 = Abid | first2 = A | last3 = White | first3 = DR | last4 = Johnson | first4 = CA | last5 = Ismail | first5 = M | last6 = Khan | first6 = A | last7 = Ayub | first7 = Q | last8 = Sultana | first8 = S | last9 = Maher | first9 = ER | last10 = Mehdi | first10 = SQ| year=2007 | s2cid=28946327 }}

When caused by mutations in the COL18A1 gene it is called Knobloch syndrome type 1.{{cite web|url=https://www.omim.org/entry/267750|title=OMIM Entry - # 267750 - Knobloch syndrome 1; KNO1|work=www.omim.org|access-date=24 February 2018}} The genes causing types II and III have yet to be identified.{{cn|date=November 2020}}

Knobloch syndrome is also characterised by cataracts, dislocated lens with skull defects such as occipital encephalocele and occipital aplasia.{{cite journal | last1 = Aldahmesh | first1 = M. A. | last2 = Khan | first2 = A. O. | last3 = Mohamed | first3 = J. Y. | last4 = Alkuraya | first4 = H. | last5 = Ahmed | first5 = H. | last6 = Bobis | first6 = S. | last7 = Al-Mesfer | first7 = S. | last8 = Alkuraya | first8 = F. S. | year = 2011| title = Identification of ADAMTS18 as a gene mutated in Knobloch syndrome | journal = J. Med. Genet. | volume = 48 | issue = 9| pages = 597–601 | pmid = 21862674 | doi=10.1136/jmedgenet-2011-100306| s2cid = 22473497 }} Encephalocele is a neural 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).{{cite book|last1=Dorland's|title=Dorland's Illustrated Medical Dictionary|date=2012|publisher=Elsevier Saunders|isbn=978-1-4160-6257-8|page=613|edition=32nd}}

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|date=March 2019}}