Knobloch syndrome

Knobloch syndrome is a rare genetic disorder presenting severe eyesight problems and often a defect in the skull. 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.^[1] Extreme myopia (near-sightedness) is a common feature.^[2]

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.^[3] There are three types of Knobloch syndrome. When caused by mutations in the COL18A1 gene it is called Knobloch syndrome type 1.^[4] The genes causing types II and III have yet to be identified.

Knobloch syndrome is also characterised by cataracts, dislocated lens with skull defects such as occipital encephalocele and occipital aplasia.^[5] 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).^[6] 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.

It is named after Knobloch who first described the syndrome in 1971.

References

↑ http://ghr.nlm.nih.gov/condition/knobloch-syndrome
↑ http://ghr.nlm.nih.gov/condition/knobloch-syndrome
↑ http://ghr.nlm.nih.gov/condition/knobloch-syndrome
↑ http://www.omim.org/entry1267750
↑ Aldahmesh, M. A., Khan, A. O., Mohamed, J. Y., Alkuraya, H., Ahmed, H., Bobis, S., Al-Mesfer, S., Alkuraya, F. S. Identification of ADAMTS18 as a gene mutated in Knobloch syndrome. J. Med. Genet. 48: 597-601, 2011. [PubMed: 21862674,
↑ Dorland's (2012). Dorland's Illustrated Medical Dictionary (32nd ed.). Elsevier Saunders. p. 613. ISBN 978-1-4160-6257-8.

Congenital malformations and deformations of nervous system (Q00–Q07, 740–742)

Brain

Neural tube defect	Anencephaly Acephaly Acrania Acalvaria Iniencephaly Encephalocele Arnold–Chiari malformation

Other	Microcephaly Congenital hydrocephalus Dandy–Walker syndrome other reduction deformities Holoprosencephaly Lissencephaly Pachygyria Hydranencephaly Septo-optic dysplasia Megalencephaly CNS cyst Porencephaly Schizencephaly Polymicrogyria Bilateral frontoparietal polymicrogyria

Spinal cord

Neural tube defect	Spina bifida Rachischisis

Other	Currarino syndrome Diastomatomyelia Syringomyelia

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