Phenotype-genotype correlation in patients with typical and atypical branchio-oto-renal syndrome

Abstract

Some patients have an atypical form of branchio-oto-renal (BOR) syndrome, which does not satisfy the diagnostic criteria, despite carrying a pathogenic variant (P variant) or a likely pathogenic variant (LP variant) of a causative gene. P/LP variants phenotypic indices have yet to be determined in patients with typical and atypical BOR syndrome. We hypothesized that determining phenotypic and genetic differences between patients with typical and atypical BOR syndrome could inform such indices. Subjects were selected from among patients who underwent genetic testing to identify the cause of hearing loss. Patients were considered atypical when they had two major BOR diagnostic criteria, or two major criteria and one minor criterion; 22 typical and 16 atypical patients from 35 families were included. Genetic analysis of EYA1, SIX1, and SIX5 was conducted by direct sequencing and multiplex ligation-dependent probe amplification. EYA1 P/LP variants were detected in 25% and 86% of atypical and typical patients, respectively. Four EYA1 P/LP variants were novel. Branchial anomaly, inner ear anomaly, and mixed hearing loss were correlated with P/LP variants. Development of refined diagnostic criteria and phenotypic indices for atypical BOR syndrome will assist in effective detection of patients with P/LP variants among those with suspected BOR syndrome.

Figure 1

The pedigree of families with typical BOR syndrome and with P/LP variants. Arrows, probands; asterisks, patients with P/LP variants; crossbars, patients who underwent genetic analysis.

Figure 2

The pedigree of families with atypical BOR syndrome and with P/LP variants. For the meaning of the symbols, see the legend of Fig. 1.

Figure 3

Numbers of patients/families with P/LP variants. (a) Patients with typical and atypical BOR syndrome. (b) Families with typical and atypical BOR syndrome. **Significant difference at p < 0.01 (Fisher’s exact test). ND, P/LP variants were not detected.

Figure 4

Prevalence rates of phenotypes in patients. (a) Patients with typical or atypical BOR syndrome. (b) Patients with or without P/LP variants of EYA1. Significant difference at **p < 0.01 and *p < 0.05, respectively (Fisher’s exact test).

Figure 5

Relationship of P/LP variants with phenotypes. (a) Association of branchial anomaly with P/LP variants. (b) Relationship between P/LP variants and unilateral or bilateral branchial anomaly. (c) Association of hearing loss types with P/LP variants. (d) Association of inner ear anomalies with P/LP variants. (e) Association of ear anomalies with P/LP variants. Significant difference at **p < 0.01 and *p < 0.05, respectively (Fisher’s exact test).