Bor Syndrome

Branchiootorenal (BOR) syndrome is characterized by branchial arch anomalies (branchial clefts, fistulae, cysts), hearing impairment (malformations of the auricle with pre-auricular pits, conductive or sensorineural hearing impairment), and renal malformations (urinary tree malformation, renal hypoplasia or agenesis, renal dysplasia, renal cysts).

Epidemiology

Prevalence is 1/40,000. Renal involvement can lead to chronic renal insufficiency.

Clinical description

The expression of the disease varies widely from one family to another and among individuals of the same family. Some families do not present with renal abnormalities or a urinary tree malformation.

Etiology

The causative gene, EYA1, is located on the long arm of chromosome 8. Point mutations and deletions in EYA1 have been identified in approximately 40% of affected individuals. Mutations have also been identified in the SIX1 and SIX5 genes, the products of which interact with EYA1 to form transcription factor complexes.

Antenatal diagnosis

Prenatal testing can be proposed to families in which the disease-causing mutation has been identified, but genetic counseling is difficult because of the clinical heterogeneity between individuals.

Genetic counseling

BOR syndrome is transmitted in an autosomal dominant manner.

Management and treatment

Management of affected patients includes excision of branchial fistulae or cysts, hearing aids and education programs appropriate for the hearing impaired, and follow-up by a nephrologist. Dialysis or renal transplantation may be required.