Nephrocalcinosis, distal renal tubular acidosis and skeletal abnormality in two siblings with ROGDI-related Kohlschütter-Tönz syndrome.

Introduction: Kohlschütter-Tönz (KTS) is a rare autosomal recessive, genetically heterogeneous disorder characterized by a triad of early-onset seizures, global developmental delay or regression, and amelogenesis imperfecta of both temporary and permanent teeth. To date, 66 cases have been reported in the literature, of which 44 with genetic confirmation.

Case report: Here we report the observation of sibling pairs in a family from a small village in India who presented with nephrocalcinosis, distal renal tubular acidosis, and skeletal abnormality. Nephrocalcinosis has only been reported once before in an individual affected with KTS.

Results: Trio exome sequencing revealed a novel, homozygous, likely pathogenic variant, c.646-2_649del, in exon 9 of the ROGDI gene (NM_024589.3) in the first child. Sanger sequencing confirmed homozygosity in both children. Both parents are heterozygous carriers of the same variant.

Conclusion: Further research needs to be done to identify the exact mechanism by which ROGDI-encoded protein deficiency leads to nephrocalcinosis and distal renal tubular acidosis.