GRHPR and Hyperoxaluria: In a next step, hyperoxaluric and non-hyperoxaluric patients were screened for sequence variations in genes known to cause monogenic hyperoxaluria (AGXT, GRHPR, HOGA1; SLC26A1—MIM# 167030) and candidate genes involved in renal and intestinal oxalate homeostasis (SLC26A6, SLC26A7) by targeted next generation sequencing (tNGS).