BOR and BO Syndromes Are Allelic Defects of EYA1

Importance of clinical evaluation and molecular testing in the branchio-oto-renal (BOR) syndrome and overlapping phenotypes

“…A previously reported mutation in a BO syndrome family (no renal anomalies) in exon 4 is the only change reported outside exons 8-16 of EYA1 24. Here, we have identified a frameshift in exon 5 in a classical BOR syndrome patient with a single unilateral kidney.…”

“…Two cases of the BO syndrome with EYA1 mutations have been reported,24 but BO syndrome families not mapping to the EYA1 locus have also been reported 27. Although it is likely that the BOR and BO syndromes are allelic mutations of the EYA1 gene, other unknown genes can cause branchial arch syndromes.…”

The gene for branchio-oculo-facial syndrome does not colocalise to the EYA1-4 genes

“…4 However, the variable expression of the BOR syndrome especially with respect to renal anomalies resulted in the delineation of a BO (branchio-oto) syndrome. Recently, it was shown that BOR and BO are allelic defects of EYA1 12. Our patients do not have renal abnormalities typical of BOR syndrome, but share branchial and otological alterations found in BO and BOF syndromes.…”

“…Our patients do not have renal abnormalities typical of BOR syndrome, but share branchial and otological alterations found in BO and BOF syndromes. Intrafamilial variability in BOFS is more indicative of an allelic disorder12 than of a contiguous gene syndrome. This intrafamilial variability also illustrates the difficulty in delineating distinct syndromes based only on isolated cases.…”

Branchio-oto-renal syndrome with obstructive sleep apnoea

“…Our case did not have renal involvement and in such situations it is sometimes termed branchio-oto (BO) syndrome. Many families with BOR and BO show linkage to same EYA1 gene suggesting that they may be allelic phenotypes of mutations in this single gene 3. The EYA1 gene is expressed very early, between the 4th and 6th weeks of human development.…”