page_title: Waardenburg Syndrome Type 4A
section_title: Genetics
hierarchical_section_title: Waardenburg Syndrome Type 4A / Genetics
caption_attribution_description: English: Development of the neural tube in human embryos (Prentiss-Arey). A. An early embryo (Keibel) B. at 2 mm. (Graf Spee) C. at 2 mm. (Mall) D. at 2.7 mm (Kollmann). This is a scan of Figure 6 of the book "The anatomy of the nervous system" by Stephen Walter Ranson, with the labels redrawn.
context_page_description: Waardenburg Syndrome Type 4A is an extremely rare congenital disorder caused by a mutation in an endothelin receptor gene. It results in common Waardenburg syndrome symptoms such as abnormal hair and skin pigmentation and heterochromia, but also present with symptoms of Hirschsprung’s disease. Symptoms include abdominal pain and bowel obstruction. Waardenburg Syndrome Type 4A is the rarest among the types, appearing only once in about every 1,000,000 individuals. There have only been a total of 50 cases reported in total as of 2016.
context_section_description: Type 4 Waardenburg Syndrome is inherited in an autosomal dominant manner, but it has also been reported in recessive autosomal. The mode of inheritance is still unclear, researchers concluded that it depends on the type of mutation that affected the EDNRB gene. 
  The abnormalities seen are caused in mutation such as the studied deletion of the endothelin‐B receptor gene, which is located at chromosome 13q22.1-q31.3. There is some variation in the size of the deletion in some patients studied. The longer deletions actually led to more severe phenotypes such as retardation and bilateral hearing loss.
  EDNRB is found in the neural tube early development, and assist in the migration and specification of the enteric nervous system precursors that are present in the gut. The homozygous mutation of this gene results in deafness and abnormal cell migration in the cell as described in the Shah-Waardenburg Syndrome. Variation of mutation for the EDNRB gene can be hard to assist appropriately due to low penetrance and variation in dosages of the product. Mutation in both copies of the gene results in full phenotypes presented by patients. On the other hand, heterzygous can display isolated or minor HSCR symptoms rather than Shah-Waardenburg symptoms.
caption: The mutations in the EDNRB gene results in abnormalities in the neural tube and specification of the enteric nervous system precursors that are present in the gut.
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