Type 1
Type 1 is characterised by congenital sensorineural hearing loss, pigmentary deficiencies of the hair such as a white lock of hair (poliosis) in the front-centre of the head or premature greying, pigmentary deficiencies of the eyes such as different-coloured eyes (complete heterochromia iridum), multiple colours in an eye (sectoral heterochromia iridum) or brilliant blue eyes, patches of skin depigmentation, and a wider gap between the inner corners of the eyes called telecanthus or dystopia canthorum. Other facial features associated with type 1 can include a high nasal bridge, a flat nose tip, a unibrow (synophrys), smaller edges of the nostrils (alae) or a smooth philtrum. Type 2
The difference that defines type 2 from type 1 is that patients do not have the wider gap between the inner corners of the eyes (telecanthus/dystopia canthorum). Sensorineural hearing loss tends to be more common and more severe in this type. By far the most common gene to cause this type when mutated is MITF (classified as type 2A).
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye), a white forelock or patches of light skin. These basic features constitute type 2 of the condition; in type 1, there is also a wider gap between the inner corners of the eyes called telecanthus, or dystopia canthorum. In type 3, which is rare, the arms and hands are also malformed, with permanent finger contractures or fused fingers, while in type 4, the person also has Hirschsprungs disease. There also exist at least two types (2E and PCWH) that can result in central nervous system (CNS) symptoms such as developmental delay and muscle tone abnormalities.The syndrome is caused by mutations in any of several genes that affect the division and migration of neural crest cells during embryonic development (though some of the genes involved also affect the neural tube). Neural crest cells are stem cells left over after the closing of the neural tube that go on to form diverse non-CNS cells in different parts of the body, including melanocytes, various bones and cartilage of the face and inner ear and the peripheral nerves of the intestines. Type 1 is caused by a mutation in the PAX3 gene, while the gene that most often causes type 2 when mutated is MITF.