Waardenburg Syndrome, Type 2

Clinical Characteristics
Ocular Features: 

This type of Waardenburg syndrome is distinguished from type 1 and 3 (193500) by the fact that it is caused by mutations in a different gene and in the absence of dystopia canthorum.  It has been claimed that hearing loss is more common and severe in type 2 (77%) as is heterochromia of the iris (47%) while skin and hair hypopigmentation are less common.

Families with WS2A may have the full spectrum of eye findings seen in X-linked ocular albinism I (300500) including decreased acuity, photophobia, nystagmus, translucent irides, hypermetropia, and albinotic fundi with foveal hypoplasia.  Indeed, such families have been considered to have 'albinism, ocular, with sensorineural deafness' (103470).  Such families might be considered to have an autosomal dominant form of ocular albinism.

Systemic Features: 

Congenital sensorineural hearing loss is an important and common feature.  Also characteristic are the white forelock, poliosis, and hypopigmented skin patches.

Genetics

Waardenburg syndrome is an excellent example of genetic heterogeneity as types 1 and 3 (193500, 148820), 2 (193510), and 4 (277580) are all caused by mutations in different genes. 

Type 2 described here is a genetically heterogeneous autosomal dominant disorder.  WS2A is caused by a mutation in MITF (microphthalmia-associated transcription factor) (3p14.1-p12.3).  This is the same disorder described as 'Albinism, ocular, with sensorineural deafness' in OMIM (103470)  (WS2-OA).

A locus at 1p21-p13.3 is associated with WS2B (600193) and WS2C (606662) maps to 8p23.  In addition, homozygous SNAI2 mutations at 8q11 have been found in several patients with WS2D (608890) suggesting autosomal recessive inheritance but the normal parents were not studied.  Recent evidence suggests that SOX10 mutations can also play a role via MITF promoter modulation (WS2E) (611584).

Type 4 is also the result of mutations in at last three genes.

A child has been reported who was doubly heterozygous for mutations involving both MITF and PAX3.  Hypopigmentation in the scalp hair, eyebrows and eyelashes was more severe than usually seen in patients with single mutations.  In addition the face showed marked patchy pigmentation.  One parent contributed the MITF mutation and the other added the mutation in PAX3.

Treatment
Treatment Options: 

No ocular treatment is necessary but assistive hearing devices can be helpful.

References
Article Title: 

References

Yang T, Li X, Huang Q, Li L, Chai Y, Sun L, Wang X, Zhu Y, Wang Z, Huang Z, Li Y, Wu H. Double heterozygous mutations of MITF and PAX3 result in Waardenburg Syndrome with increased penetrance in pigmentary defects. Clin Genet. 2012 Feb 9. doi: 10.1111/j.1399-0004.2012.01853.x. [Epub ahead of print]

PubMedID: 22320238

Pardono E, van Bever Y, van den Ende J, Havrenne PC, Iughetti P, Maestrelli SR, Costa F O, Richieri-Costa A, Frota-Pessoa O, Otto PA. Waardenburg syndrome: clinical differentiation between types I and II. Am J Med Genet A. 2003 Mar 15;117A(3):223-35.

PubMedID: 12599185

Pingault V, Ente D, Dastot-Le Moal F, Goossens M, Marlin S, Bondurand N. Review and update of mutations causing Waardenburg syndrome. Hum Mutat. 2010 Apr;31(4):391-406. Review.

PubMedID: 20127975

Liu XZ, Newton VE, Read AP. Waardenburg syndrome type II: phenotypic findings and diagnostic criteria. Am J Med Genet. 1995 Jan 2;55(1):95-100. Review.

PubMedID: 7702105