Renal Dysfunction, Rod-Cone Dystrophy, And Sensorineural Hearing Loss Caused By A Mutation Inrrm2b

More than two decades ago, a recessive syndromic phenotype affecting kidneys, eyes, and ears, was first described in the endogamous Afrikaner population of South Africa. Using whole-exome sequencing of DNA from two affected siblings (and their carrier parents), we identified the novelRRM2Bc.786G>T variant as a plausible disease-causing mutation. TheRRM2Bgene is involved in mitochondrial integrity, and the observed change was not previously reported in any genomic database. The subsequent screening revealed the variant in two newly presenting unrelated patients, as well as two patients in our registry with rod-cone dystrophy, hearing loss, and Fanconi-type renal disease. All patients with the c.786G>T variant share an identical 1.5 Mb haplotype around this gene, suggesting a founder effect in the Afrikaner population. We present ultrastructural evidence of mitochondrial impairment in one patient, to support our thesis that thisRRM2Bvariant is associated with the renal, ophthalmological, and auditory phenotype.