Facial appearance of a boy from China with<unk>  type 1<unk>  has multiple different types with some variations in symptoms, and symptoms can vary among those with the same type. The two features consistent across all types of<unk>  are some degree of congenital sensorineural hearing loss and some degree of pigmentation deficiencies, most consistently in the eyes. 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). If two individuals with a mutation in this gene have a child carrying both mutations (homozygous), for which there is 25% chance, additional symptoms are present in the child, such as a hole in the iris (coloboma), small eyes (microphthalmia), hardened bones (osteopetrosis), macrocephaly, albinism and deafness. There have been two known patients identified with mutations in both copies of SNAI2 (classified as type 2D); these individuals presented with<unk>  type 2 but did not have hair pigmentation deficiencies. When<unk>  type 2 is caused by a mutation in SOX10 (classified as type 2E), it can on some occasions present with multiple neurological symptoms. These can include developmental delay, early childhood nystagmus, increased muscle tone, white matter anomalies or hypomyelination in the brain, autistic-like behaviour and the underdevelopment or complete absence of many inner-ear structures such as the vestibular system or cochlea. Lack of a sense of smell (anosmia) due to a missing olfactory bulb in the brain may also be present. Type 3 Also known as Klein–Waardenburg syndrome, or<unk> –Klein syndrome, type 3 has the same symptoms as type 1 (and is caused by mutations in the same gene) but has additional symptoms that affect the arms and hands. These can include joint contractures of the fingers (camptodactyly), due to underdeveloped muscles, as well as fused digits (syndactyly) or winged scapulae. Microcephaly and developmental delay are also possible. Type 4 Also known as Shah–Waardenburg syndrome, or<unk> –Shah syndrome, type 4 has most of the same features as type 2 (i.e. no telecanthus, or apparent wider eye gap), but with the addition of Hirschsprung's disease, which is a congenital lack of nerves in the intestines leading to bowel dysfunction. Additionally, hearing loss is not as common as in type 2. Rarely, cleft lip has been reported in this form of<unk> . Type 4 can also be caused by a mutation in SOX10 (the same gene as in type 2E), in which it is known as type 4C; hearing loss is very common and severe in this type. PCWH A mutation in SOX10, the gene involved in type 2E and type 4C, can sometimes result in the symptoms of both types (neurological symptoms, as sometimes seen in type 2E, and Hirschsprung's disease, as seen in type 4). When this happens, it is called peripheral demyelinating neuropathy–central dysmyelinating leukodystrophy–Waardenburg syndrome–Hirschsprung disease (PCWH).
Waardenburg syndrome
Van Den Bosch syndrome
Alder–Reilly anomaly
Wildervanck syndrome
Aagenaes syndrome
Pelger–Huët anomaly
Singleton Merten syndrome
Koolen–De Vries syndrome