1. NGS panel - Genetic testing for Waardenburg syndrome

Waardenburg syndrome

June 29, 2017

Clinical features

Waardenburg syndrome (WS) is an auditory-pigmentary disorder characterized by congenital sensorineural hearing loss and pigmentary abnormalities of the iris, skin and hair, and with dystopia canthorum.

There are four known types of Waardenburg syndrome which are distinguished by their physical characteristics and sometimes by their genetic cause:

  • Types I and II have very similar features, although people with type I almost always have widely spaced eyes and preserved hearing in comparison to type II
  • Type III (also known as Klein-Waardenburg syndrome) in addition to hearing loss and changes in pigmentation includes abnormalities of the upper limbs
  • Type IV (also known as Waardenburg-Shah syndrome) has signs and symptoms of both Waardenburg syndrome and Hirschsprung disease, an intestinal disorder that causes severe constipation of the intestine.

The major clinical features of Waardenburg syndrome are very heterogeneous and may vary among affected individuals and even among people in the same affected family1. An individual must have two major criteria or one major plus two minor criteria to be considered to be affected with Waardenburg syndrome1:

Major criteria for diagnostics of Waardenburg syndrome:

  • Congenital sensorineural hearing loss
  • White forelock, hair hypopigmentation
  • Pigmentation abnormality of the iris
  • Complete heterochromia iridum (irides of different color)
  • Partial/segmental heterochromia (two different colors in same iris, typically brown and blue)
  • Hypoplastic blue irides or brilliant blue irides
  • Dystopia canthorum, W index >1.95 *
  • Affected first-degree relative

* Note: The measurements necessary to calculate the W index (in mm) are as follows: inner canthal distance (a), interpupillary distance (b), and outer canthal distance (c). Calculate X = (2a – (0.2119c + 3.909))/c Calculate Y = (2a – (0.2479b + 3.909))/b Calculate W = X + Y + a/b

Minor criteria for diagnostics of Waardenburg syndrome:

  • Skin hypopigmentation (congenital leukoderma)
  • Synophrys/medial eyebrow flare
  • Broad/high nasal root, prominent columella
  • Hypoplastic alae nasi
  • Premature gray hair (age <30 years)

Type I Waardenburg syndrome is characterized by evidence of dystopia canthorum and the full symptomatology of the disease1. Individuals with type I Waardenburg syndrome also have a narrow nose, marked hypoplasia of the nasal bone, short philtrum, and short and retropositioned maxilla. A discriminant analysis revealed that the inner intercanthic distance, philtrum length, lower facial height, and nasal bone length were discriminating parameters of Waardenburg syndrome. Convergent strabismus and reduced visibility of the medial sclera is observed. The head circumference, clivus length, and facial depth are smaller in affected individuals with this syndrome.

Individuals with type II Waardenburg syndrome are a heterogeneous group with normally located canthi (without dystopia canthorum). Sensorineural hearing loss (77%) and heterochromia iridium (47%) are the two most important diagnostic indicators for this type2. Other clinical manifestations (e.g. white forelock, skin patches) are more frequent in type I.

Type III Waardenburg syndrome (Klein-Waardenburg syndrome) is similar to type I but is also characterized by musculoskeletal abnormalities 3,4. Some individuals with type III Waardenburg syndrome are homozygotes. Other clinical manifestations of type III comprise the full symptomatology of the disease plus mental retardation, microcephaly, and severe skeletal anomalies.

Type IV Waardenburg syndrome (Shah-Waardenburg syndrome) is the association of Waardenburg syndrome with congenital aganglionic megacolon (Hirschsprung disease)5. Hirschsprung disease affects 1 neonates per 5000 births1,7.

The features of Waardenburg syndrome affect an estimated 1 in 20,000-40,000 people. It accounts for 3% of all cases of congenital hearing loss8. Types I and II are the most common forms of Waardenburg syndrome, while types III and IV are rare1,7,8.

Waardenburg syndrome is caused by abnormal migration or differentiation of neural crest cells during embryonic development. Several disease-causing genes have been identified so far (see Table).


Overview of genes included in Waardenburg syndrome panel offered by CENTOGENE

Gene
(OMIM)
chr.locus
Protein
Frequency of mutations Associated/allelic disorders
EDN3
(131242)
20q13.32 Less common 1,8
5% for Hirschprung disease 11
Waardenburg syndrome, type 4B (613265); {Hirschsprung disease, susceptibility to, 4} (613712); Central hypoventilation syndrome, congenital (209880)
EDNRB
(131244)
13q22.3 Common 1, 9
3%-7% for Hirschprung disease 11
Waardenburg syndrome, type 4A (277580); {Hirschsprung disease, susceptibility to, 2} (600155); ABCD syndrome (600501)
MITF
(156845)
3p13 10%-20% of individuals with WS2 9 Waardenburg syndrome, type 2A (193510); COMMAD syndrome (617306); Tietz albinism-deafness syndrome (103500); Waardenburg syndrome/ocular albinism, digenic (103470); {Melanoma, cutaneous malignant, susceptibility to, 8} (614456)
PAX3
(606597)
2q36.1 >90% 1, 3 Waardenburg syndrome, type 1 (193500); Waardenburg syndrome, type 3 (148820); Craniofacial-deafness-hand syndrome (122880); Rhabdomyosarcoma 2, alveolar (268220)
SNAI2
(602150)
8q11.21 2 patients 1 Waardenburg syndrome, type 2D (608890); Piebaldism (172800)
TYR
(606933)
11q14.3 Very common in OCA1A and OCA2 10 Waardenburg syndrome/albinism, digenic (103470); Albinism, oculocutaneous, type IA (203100); Albinism, oculocutaneous, type IB (606952); [Skin/hair/eye pigmentation 3, blue/green eyes] (601800)

There is no cure for Waardenburg syndrome. However, symptomatic management should include supportive management of the hearing impairment and surgical treatment for associated Hirschsprung disease.

CENTOGENE is offering full gene sequencing and deletion/duplication analysis for the Waardenburg syndrome panel (genes: ECE1, EDN3, EDNRB, GDNF, KIAA1279, NRG1, NRTN, RET, SOX10, ZEB2). Each gene in these panel can also be ordered individually as a single gene test.


Differential diagnosis

The differential diagnosis of Waardenburg syndrome-related disorders – depending on the major symptoms in the initial case – includes the following diseases:

  • Piebaldism
  • Woolf syndrome (the association of albinismus circumscriptus and deafmutism without other features of Waardenburg syndrome)
  • Hirschprung disease, nonsyndromic, isolated intestinal aganglionosis
  • ABCD or BADS syndromes

Testing strategy

CENTOGENE offers advanced, fast and cost-effective strategy to test large NGS panels and diagnose complex phenotypes based on the PCR-free whole genome sequencing and NGS technology. This approach offers an unparalleled advantage by reducing amplification/capture biases and provides sequencing of entire gene at a more uniform coverage.

To confirm/establish the diagnosis, CENTOGENE offers the following testing strategy for Waardenburg syndrome using NGS Panel Genomic targeted towards this specific phenotype:

Step 1: Whole genome sequencing from a single filter card. The sequencing covers the entire genic region (coding region, exon/intron boundaries, intronic and promoter) for all the genes included in the Waardenburg panel. Copy Number Variants analysis derived from NGS data is also included.

Step 2: If no mutation is identified after analysis of the Waardenburg syndrome panel, based on the approval and consent, we further recommend to continue the bioinformatics analysis of the data obtained by whole genome sequencing to cover genes that are either implicated in an overlapping phenotype or could be involved in a similar pathway but not strongly clinically implicated based on the current information in literature.


Referral reasons

The following individuals are candidates for Waardenburg syndrome panel testing:

  • Individuals with a family history of Waardenburg syndrome and presentation of the most common symptoms including sensorineural hearing loss and pigmentary disturbances of the iris, hair, and skin, along with dystopia canthorum.
  • Individuals without a positive family history, but with symptoms resembling Waardenburg syndrome.
  • Individuals (infants) with a negative but suspected family history of Waardenburg syndrome, in order to perform proper genetic counseling.

Test utility

Sequencing, deletion/duplication of the Waardenburg syndrome panel genes should be performed in all individuals suspected of having Waardenburg syndrome and suspected phenotypes. In parallel, other genes reported to be related with this clinical phenotype should also be analyzed for the presence of mutations, due to the overlap in many clinical features caused by those particular genes.

Confirmation of a clinical diagnosis through genetic testing can allow for genetic counseling and may direct medical management. Genetic counseling can provide a patient and/or family with the natural history of the Waardenburg syndrome and related disorders, identify at-risk family members, provide disease risks as well as appropriate referral for patient support and/or resources.


More information on CENTOGENE´s Waardenburg syndrome panel can be found in our genetic test catalogue.