Waardenburg syndrome
Waardenburg syndrome is a group of rare genetic conditions. It is characterised by congenital hearing loss and pigmentation deficiencies. These can include bright blue eyes, a white forelock or patches of light skin. In type 1, there is also a wider gap between the inner corners of the eyes. Most types are autosomal dominant and estimated prevalence is 1 in 42,000.
About Waardenburg syndrome in brief
Waardenburg syndrome is a group of rare genetic conditions. It is characterised by congenital hearing loss and pigmentation deficiencies. These can include bright blue eyes, a white forelock or patches of light skin. In type 1, there is also a wider gap between the inner corners of the eyes. The syndrome is caused by mutations in any of several genes. Most types are autosomal dominant and estimated prevalence is 1 in 42,000. Types 1 and 2 are the most common, comprising approximately half and a third of cases respectively, while type 4 comprises a fifth and type 3 less than 2% of cases. There also exist at least two types that can result in central nervous system symptoms such as developmental delay and muscle tone abnormalities. Waardenburg–Klein syndrome, type 3 has the same symptoms as type 1 but has additional symptoms that affect the hands and arms. These include joint contractures due to the under-development of the muscles, as well as the absence of many inner-ear structures such as the vestibular or cochlea. Lack of a sense of smell due to a missing olfactory bulb in the brain may also be present. Also known as Klein–Waardenberg syndrome, this is a condition where the brain bulb is missing in one or more parts of the brain. It can also cause albinism, macrocephaly, deafness and other neurological conditions. The most common gene to cause this type when mutated is MITF.
If two individuals with a mutation in this gene have a child carrying both mutations, for which there is 25% chance, additional symptoms are present in the child, such as a hole in the iris, small eyes, hardened bones and hypomyelination in thebrain. The condition is named after Dutch ophthalmologist and geneticist Petrus Johannes Waardenberg, who described it in 1951. Its subtypes were progressively discovered in the following decades and had genes attributed to them mostly in the 1990s and 2000s. Type 1 is caused. by a mutation in the PAX3 gene, while the gene that most often causes type 2 when mutated isMITF. Type 3 is a more severe presentation of type 1 and is caused in the same way as type 2. Type 4 is most often caused by a mutated gene in SOX10, and some of these have been given their own lettered subtypes, including type 3 and type 4 of type 2 of the condition. Type 5 is a rare condition that causes the person to have Hirschsprung’s disease, which is a congenital lack of nerves in the intestines leading to bowel dysfunction. The person also has a high nasal bridge, a flat nose tip, a unibrow, smaller edges of the nostrils or a smooth philtrum. The difference that defines type 2 from type 1 is that patients do not have the wider gap or dystopia canthorum. Sensorineural hearing loss tends to be more common and more severe in this type.
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This page is based on the article Waardenburg syndrome published in Wikipedia (as of Dec. 10, 2020) and was automatically summarized using artificial intelligence.
