Nephrocalcinosis in hyperphosphataemic familial tumoural calcinosis in a 36-year-old woman

Nephrocalcinosis is characterised by the deposition of calcium oxalate or calcium phosphate in the tubulointerstitial regions of the kidney. Rarely, disturbances in phosphate homeostasis in the course of hyperphosphataemic familial tumoural calcinosis can be the cause of nephrocalcinosis. The main symptoms of this condition include ectopic calcifications, hyperostosis, and dental abnormalities. In this article, we present the clinical and genetic description of a case involving a 36-year-old woman in whom nephrocalcinosis was incidentally discovered and subsequently led to the diagnosis of hyperphosphataemic familial tumoural calcinosis. In the course of the molecular diagnostic process, whole-exome short-read sequencing detected a heterozygous in-frame deletion (c.1093_1095del; p.Gly365del) in the GALNT3 gene, while long-read single-molecule real-time sequencing identified a complex indel (c.1382_1388delins814) in GALNT3 exon 7. To the authors’ knowledge, this is the first described case of a patient with this specific mutation.