Right hypoplastic kidney

A 21-year-old woman was referred to our hospital because of proteinuria and mild renal dysfunction. Her serum creatinine concentration was 1.10 mg/dl and estimated glomerular filtration rate was 53.9 ml/min per 1.73 m2. The urinary analysis revealed 2+ protein. Abdominal computerized tomography (CT) showed right renal hypoplasia (Figure 1). In addition, she had mixed hearing disturbance and a history of surgeries for correction of left cervical branchial fistulae and bilateral preauricular pits (Figure 2, left ear). Her temporal bone CT presented bilateral inner ear malformation. On the basis of these findings, she was suspected to have branchio-oto-renal (BOR) syndrome, although she has no family history on renal dysfunction and hearing disturbance. The BOR syndrome is an autosomal dominant disorder, which is characterized by the association of branchial anomalies (preauricular pits and branchial fistulae or cysts), otic anomalies affecting the outer, middle, and/or inner ear, which frequently lead to hearing disturbance (sensorineural, conductive, or mixed), and a wide spectrum of renal anomalies ranging from mild hypoplasia to lethal bilateral renal aplasia. The prevalence is approximately 1 in 40,000. The BOR syndrome is associated with several genetic mutations in EYA1, SIX1, SALL1, and SIX5. Because of disagreement towards conducting gene analysis from the patient's family, we performed gene analysis of only the patient with informed consent. DNA sequencing analysis revealed a heterozygous mutation, c.880 C>T, p.R294X, in exon 10 of the EYA1 gene. The BOR syndrome should be taken into consideration on the differential diagnosis in young adult patients with renal dysfunction and hearing disturbance.