Oculoauricular Syndrome

Clinical Characteristics
Ocular Features: 

This rare malformation syndrome affects primarily the eyes and ears.  The globes are small and usually have colobomas of both anterior and posterior segments.  The corneas likewise are small and often have opacities.  The anterior segment is dysplastic with anterior and/or posterior synechiae.  Glaucoma may be present.  The lenses may be small and often become cataractous.  There is a progressive rod-cone dystrophy associated with a pigmentary retinopathy.  Chorioretinal lacunae have been seen in the equatorial region.  The retinal degeneration is progressive, beginning with rod dysfunction but followed by deterioration of all receptors.  The onset in early childhood results in poor vision and nystagmus. 

Systemic Features: 

The external ears are abnormal.  The earlobes may have colobomas or may be aplastic.  The intertragic notch is often underdeveloped.  Audiograms and vestibular function tests, however, show normal function and MRI of the middle and inner ears likewise reveals no anatomic abnormalities.       

Among the few patients reported, dental anomalies, spina bifida oculta, and mild dyscrania have been noted in individual patients.

Genetics

This rare disorder has been reported in only a few families.  Based on parental consanguinity and homozygosity of mutations in the HMX1 gene (4p16.1) in affected sibs, this is an autosomal recessive disorder.  In one family there was a homozygous 26 bp deletion and in another a homozygous missense mutation.  The parents are heterozygous for the deletion.

HMX1 is a homeobox gene and the deletion abolishes its function by establishing a stop codon at position 112.

Treatment
Treatment Options: 

No treatment is available for the extraocular malformations.  Glaucoma treatment and cataract surgery should be considered although permanent visual rehabilitation is unlikely given the progressive nature of the rod-cone dystrophy.

References
Article Title: 

References

Gillespie RL, Urquhart J, Lovell SC, Biswas S, Parry NR, Schorderet DF, Lloyd IC, Clayton-Smith J, Black GC. Abrogation of HMX1 Function Causes Rare Oculoauricular Syndrome Associated With Congenital Cataract, Anterior Segment Dysgenesis, and Retinal Dystrophy. Invest Ophthalmol Vis Sci. 2015 Jan 8;56(2):883-91.

PubMedID: 25574057

Vaclavik V, Schorderet DF, Borruat FX, Munier FL. Retinal Dystrophy In The Oculo-auricular Syndrome Due to HMX1 Mutation. Ophthalmic Genet. 2011 Jun;32(2):114-7.

PubMedID: 21417677

Schorderet DF, Nichini O, Boisset G, Polok B, Tiab L, Mayeur H, Raji B, de la Houssaye G, Abitbol MM, Munier FL. Mutation in the human homeobox gene NKX5-3 causes an oculo-auricular syndrome. Am J Hum Genet. 2008 May;82(5):1178-84.

PubMedID: 18423520