Waardenburg syndrome

Waardenburg syndrome (also Waardenburg­ Shah Syndrome, Waardenburg-Klein syndrome, Mende's syndrome II, Van der Hoeve-Halbertsma-Waardenburg syndrome, Ptosis-Epicanthus syndrome, Van der Hoeve-Halbertsma-Gualdi syndrome, Waardenburg type Pierpont,[5] Van der Hoeve-Waardenburg-Klein syndrome, Waardenburg's syndrome II and Vogt’s syndrome.) is a rare genetic disorder most often characterized by varying degrees of deafness, minor defects in structures arising from the neural crest, and pigmentation anomalies.

It was first described in 1951

Eponyms and classification
Waardenburg syndrome is named after Dutch ophthalmologist Petrus Johannes Waardenburg (1886–1979), who described the syndrome in detail in 1951. The condition he described is now categorized as WS1. Swiss ophthalmologist David Klein also made contributions towards the understanding of the syndrome.

WS2 was identified in 1971, to describe cases where "dystopia canthorum" did not present. WS2 is now split into subtypes, based upon the gene responsible.

Other types have been identified, but they are less common.

Signs and symptoms
There are five major and five minor diagnostic criteria for Waardenburg syndrome.

Major:
 * sensorineural hearing loss
 * iris pigmentary abnormality (two eyes different color or iris bicolor or characteristic brilliant blue iris)
 * hair hypopigmentation (white forelock or white hairs at other sites on the body)
 * dystopia canthorum (lateral displacement of inner canthi)
 * first‐degree relative previously diagnosed with Waardenburg syndrome

Minor:
 * skin hypopigmentation (congenital leukoderma/white skin patches)
 * medial eyebrow flare (synophrys)
 * broad nasal root
 * hypoplasia alae nasi
 * premature graying of the hair (before age 30).

Epidemiology
The overall incidence is ~1/42,000 — 1/50,000 people. Types I and II are the most common types of the syndrome, whereas types III and IV are rare. Type 4 is also known as Waardenburg‐Shah syndrome (association of Waardenburg syndrome with Hirschsprung disease).

Type 4 is rare with only 48 cases reported up to 2002.

About 1 in 30 students in schools for the deaf have Waardenburg syndrome. All races and both sexes are affected equally. The highly variable presentation of the syndrome makes it difficult to arrive at precise figures for its prevalence.

Classification
Subtypes of the syndrome are traceable to different genetic variations:

Symptoms


Symptoms vary from one type of the syndrome to another and from one patient to another, but they include:
 * Very pale or brilliantly blue eyes, eyes of two different colors (complete heterochromia), or eyes with one iris having two different colours (sectoral heterochromia);
 * A forelock of white hair (poliosis), or premature graying of the hair;
 * Appearance of wide-set eyes due to a prominent, broad nasal root (dystopia canthorum)—particularly associated with type I) also known as telecanthus;
 * Moderate to profound hearing loss (higher frequency associated with type II);
 * A low hairline and eyebrows that touch in the middle.
 * Patches of white pigmentation on the skin have been observed in some people. Sometimes, abnormalities of the arms, associated with type III, have been observed.
 * Type IV may include neurologic manifestations.

Waardenburg syndrome has also been associated with a variety of other congenital disorders, such as intestinal and spinal defects, elevation of the scapula, and cleft lip and palate. Sometimes this is concurrent with Hirschsprung disease.

Inheritance
This condition is usually inherited in an autosomal dominant pattern, which means one copy of the altered gene is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition. A small percentage of cases result from new mutations in the gene; these cases occur in people with no history of the disorder in their family.

Some cases of type II and type IV Waardenburg syndrome appear to have an autosomal recessive pattern of inheritance, which means two copies of the gene must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.

Treatment
There is currently no treatment or cure for Waardenburg syndrome. The symptom most likely to be of practical importance is deafness, and this is treated as any other irreversible deafness would be. In marked cases there may be cosmetic issues. Other abnormalities (neurological, structural, Hirschsprung disease) associated with the syndrome are treated symptomatically.

In animals
Waardenburg syndrome is known to occur in ferrets. The affected animal will usually have a small white stripe along the top of its head or a solid white head and a somewhat, although barely noticeably, flatter skull than normal ferrets. As a ferret's sense of hearing is poor to begin with it is not easily noticeable except for when the affected animal does not react to loud noises that non-affected ones will respond to. As the disorder is easily spread to offspring, the affected animal will not be used for breeding by private, reputable breeders, although it may still be neutered and sold as a pet. However, largely as a result of mass-breeding, 75% of ferrets with a blaze or white head sold from pet stores are deaf.

In Popular Culture
In the season 6 episode of Bones (TV Series), 'The Signs in the Silence', the team must solve a case in which the suspected killer has Waardenburg syndrome.

Enzo Macleod, protagonist of Peter May's series The Enzo Files, has Waardenburg syndrome. His eyes are different colors and he has a white streak in his hair. See pp. 17-18 of "Extraordinary People" (2006) by Peter Mays.